[V23,2/3] misc: dcc: Add driver support for Data Capture and Compare unit(DCC)

Commit Message

Souradeep Chowdhury May 5, 2023, 6:36 a.m. UTC

The DCC is a DMA Engine designed to capture and store data during system
crash or software triggers. The DCC operates based on user inputs via
the debugfs interface. The user gives addresses as inputs and these
addresses are stored in the dcc sram. In case of a system crash or a
manual software trigger by the user through the debugfs interface, the
dcc captures and stores the values at these addresses. This patch
contains the driver which has all the methods pertaining to the debugfs
interface, auxiliary functions to support all the four fundamental
operations of dcc namely read, write, read/modify/write and loop. The
probe method here instantiates all the resources necessary for dcc to
operate mainly the dedicated dcc sram where it stores the values. The
DCC driver can be used for debugging purposes without going for a reboot
since it can perform software triggers as well based on user inputs.

Also update the documentation for debugfs entries which explains the
functionalities of each debugfs file that has been created for dcc.
Update the documentation to reflect new module name for dcc.

The following is the justification of using debugfs interface over the
other alternatives like sysfs/ioctls

i) As can be seen from the debugfs attribute descriptions, some of the
debugfs attribute files here contains multiple arguments which needs to
be accepted from the user. This goes against the design style of sysfs.

ii) The user input patterns have been made simple and convenient in this
case with the use of debugfs interface as user doesn't need to shuffle
between different files to execute one instruction as was the case on
using other alternatives.

Signed-off-by: Souradeep Chowdhury <[e-mail]>
Reviewed-by: Alex Elder <[e-mail]>
---
 Documentation/ABI/testing/debugfs-driver-dcc |   10 +-
 drivers/misc/Kconfig                         |    9 +
 drivers/misc/Makefile                        |    1 +
 drivers/misc/qcom-dcc.c                      | 1325 ++++++++++++++++++
 4 files changed, 1340 insertions(+), 5 deletions(-)
 create mode 100644 drivers/misc/qcom-dcc.c

Comments

Trilok Soni May 24, 2023, 5:10 a.m. UTC | #1

On 5/4/2023 11:36 PM, Souradeep Chowdhury wrote:
> The DCC is a DMA Engine designed to capture and store data during system
> crash or software triggers. The DCC operates based on user inputs via
> the debugfs interface. The user gives addresses as inputs and these
> addresses are stored in the dcc sram. In case of a system crash or a
> manual software trigger by the user through the debugfs interface, the
> dcc captures and stores the values at these addresses. This patch
> contains the driver which has all the methods pertaining to the debugfs
> interface, auxiliary functions to support all the four fundamental
> operations of dcc namely read, write, read/modify/write and loop. The
> probe method here instantiates all the resources necessary for dcc to
> operate mainly the dedicated dcc sram where it stores the values. The
> DCC driver can be used for debugging purposes without going for a reboot
> since it can perform software triggers as well based on user inputs.
> 
> Also update the documentation for debugfs entries which explains the
> functionalities of each debugfs file that has been created for dcc.
> Update the documentation to reflect new module name for dcc.
> 
> The following is the justification of using debugfs interface over the
> other alternatives like sysfs/ioctls
> 
> i) As can be seen from the debugfs attribute descriptions, some of the
> debugfs attribute files here contains multiple arguments which needs to
> be accepted from the user. This goes against the design style of sysfs.
> 
> ii) The user input patterns have been made simple and convenient in this
> case with the use of debugfs interface as user doesn't need to shuffle
> between different files to execute one instruction as was the case on
> using other alternatives.
> 
> Signed-off-by: Souradeep Chowdhury <[e-mail]>
> Reviewed-by: Alex Elder <[e-mail]>


Bjorn, do you have any remaining comments here? Are you going to provide 
  your Reviewed-by here and other patches?

If there are no comments then I would like this series to be picked by 
the maintainer you suggest.

---Trilok Soni

Trilok Soni May 31, 2023, 4:17 p.m. UTC | #2

On 5/23/2023 10:10 PM, Trilok Soni wrote:
> On 5/4/2023 11:36 PM, Souradeep Chowdhury wrote:
>> The DCC is a DMA Engine designed to capture and store data during system
>> crash or software triggers. The DCC operates based on user inputs via
>> the debugfs interface. The user gives addresses as inputs and these
>> addresses are stored in the dcc sram. In case of a system crash or a
>> manual software trigger by the user through the debugfs interface, the
>> dcc captures and stores the values at these addresses. This patch
>> contains the driver which has all the methods pertaining to the debugfs
>> interface, auxiliary functions to support all the four fundamental
>> operations of dcc namely read, write, read/modify/write and loop. The
>> probe method here instantiates all the resources necessary for dcc to
>> operate mainly the dedicated dcc sram where it stores the values. The
>> DCC driver can be used for debugging purposes without going for a reboot
>> since it can perform software triggers as well based on user inputs.
>>
>> Also update the documentation for debugfs entries which explains the
>> functionalities of each debugfs file that has been created for dcc.
>> Update the documentation to reflect new module name for dcc.
>>
>> The following is the justification of using debugfs interface over the
>> other alternatives like sysfs/ioctls
>>
>> i) As can be seen from the debugfs attribute descriptions, some of the
>> debugfs attribute files here contains multiple arguments which needs to
>> be accepted from the user. This goes against the design style of sysfs.
>>
>> ii) The user input patterns have been made simple and convenient in this
>> case with the use of debugfs interface as user doesn't need to shuffle
>> between different files to execute one instruction as was the case on
>> using other alternatives.
>>
>> Signed-off-by: Souradeep Chowdhury <[e-mail]>
>> Reviewed-by: Alex Elder <[e-mail]>
> 
> 
> Bjorn, do you have any remaining comments here? Are you going to provide 
>   your Reviewed-by here and other patches?
> 
> If there are no comments then I would like this series to be picked by 
> the maintainer you suggest.
> 

Gentle reminder again here. I would like to make some progress on DCC 
discussion here. Is it ready to be picked up by Bjorn or Arnd?

---Trilok Soni

Greg Kroah-Hartman June 15, 2023, 10:33 a.m. UTC | #3

On Thu, May 04, 2023 at 11:36:22PM -0700, Souradeep Chowdhury wrote:
> +/**
> + * struct dcc_config_entry - configuration information related to each dcc instruction
> + * @base:                    Base address of the register to be configured in dcc

Why is this a u32 and not a bigger size?

> + * @offset:                  Offset to the base address to be configured in dcc
> + * @len:                     Length of the address in words to be configured in dcc

What is a "word" here, 16 bits?

> + * @loop_cnt:                The number of times to loop on the register address in case
> +				of loop instructions
> + * @write_val:               The value to be written on the register address in case of
> +				write instructions
> + * @mask:                    Mask corresponding to the value to be written in case of
> +				write instructions
> + * @apb_bus:                 Type of bus to be used for the instruction, can be either
> +				'apb' or 'ahb'

How can a bool be either "apb" or "ahb"?

> + * @desc_type:               Stores the type of dcc instruction
> + * @list:                    This is used to append this instruction to the list of
> +				instructions
> + */
> +struct dcc_config_entry {
> +	u32				base;
> +	u32				offset;
> +	u32				len;
> +	u32				loop_cnt;
> +	u32				write_val;
> +	u32				mask;
> +	bool				apb_bus;
> +	enum dcc_descriptor_type	desc_type;
> +	struct list_head		list;
> +};
> +
> +/**
> + * struct dcc_drvdata - configuration information related to a dcc device
> + * @base:		Base Address of the dcc device
> + * @dev:		The device attached to the driver data
> + * @mutex:		Lock to protect access and manipulation of dcc_drvdata
> + * @ram_base:		Base address for the SRAM dedicated for the dcc device
> + * @ram_size:		Total size of the SRAM dedicated for the dcc device
> + * @ram_offset:		Offset to the SRAM dedicated for dcc device
> + * @mem_map_ver:	Memory map version of DCC hardware
> + * @ram_cfg:		Used for address limit calculation for dcc
> + * @ram_start:		Starting address of DCC SRAM
> + * @sram_dev:		Miscellaneous device equivalent of dcc SRAM
> + * @cfg_head:		Points to the head of the linked list of addresses
> + * @dbg_dir:		The dcc debugfs directory under which all the debugfs files are placed
> + * @nr_link_list:	Total number of linkedlists supported by the DCC configuration
> + * @loop_shift:		Loop offset bits range for the addresses
> + * @enable_bitmap:	Bitmap to capture the enabled status of each linked list of addresses

You use a pointer for a bitmap?

> + */
> +struct dcc_drvdata {
> +	void __iomem		*base;
> +	void __iomem            *ram_base;
> +	struct device		*dev;
> +	struct mutex		mutex;
> +	size_t			ram_size;
> +	size_t			ram_offset;
> +	int			mem_map_ver;

u64?

> +	unsigned int		ram_cfg;
> +	unsigned int		ram_start;
> +	struct miscdevice	sram_dev;
> +	struct list_head	*cfg_head;
> +	struct dentry		*dbg_dir;
> +	size_t			nr_link_list;

"nr"?

> +	u8			loop_shift;
> +	unsigned long		*enable_bitmap;
> +};
> +
> +struct dcc_cfg_attr {
> +	u32	addr;
> +	u32	prev_addr;
> +	u32	prev_off;
> +	u32	link;
> +	u32	sram_offset;
> +};
> +
> +struct dcc_cfg_loop_attr {
> +	u32	loop_cnt;
> +	u32	loop_len;
> +	u32	loop_off;
> +	bool    loop_start;
> +};
> +
> +static inline u32 dcc_status(int version)
> +{
> +	return version == 1 ? 0x0c : 0x1c;
> +}
> +
> +static inline u32 dcc_list_offset(int version)
> +{
> +	if (version == 1)
> +		return 0x1c;
> +	else if (version == 2)
> +		return 0x2c;
> +	else
> +		return 0x34;
> +}
> +
> +static inline void dcc_list_writel(struct dcc_drvdata *drvdata,
> +				   u32 ll, u32 val, u32 off)
> +{
> +	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
> +
> +	writel(val, drvdata->base + ll * DCC_LL_OFFSET + offset);
> +}
> +
> +static inline u32 dcc_list_readl(struct dcc_drvdata *drvdata, u32 ll, u32 off)
> +{
> +	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
> +
> +	return readl(drvdata->base + ll * DCC_LL_OFFSET + offset);
> +}
> +
> +static void dcc_sram_write_auto(struct dcc_drvdata *drvdata,
> +				u32 val, u32 *off)
> +{
> +	/* If the overflow condition is met increment the offset
> +	 * and return to indicate that overflow has occurred
> +	 */
> +	if (unlikely(*off > drvdata->ram_size - 4)) {

If you can not measure the difference in userspace when using
likely/unlikely, then never use it as the compiler and CPU will do it
better for you.

> +		*off += 4;
> +		return;
> +	}
> +
> +	writel(val, drvdata->ram_base + *off);
> +
> +	*off += 4;
> +}
> +
> +static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
> +{
> +	void __iomem *addr;
> +	int i;
> +	u32 status;
> +	u32 ll_cfg;
> +	u32 tmp_ll_cfg;
> +	u32 val;
> +	int ret = 0;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	for (i = 0; i < drvdata->nr_link_list; i++) {
> +		if (!test_bit(i, drvdata->enable_bitmap))
> +			continue;
> +		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
> +		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
> +		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
> +		dcc_list_writel(drvdata, 1, i, DCC_LL_SW_TRIGGER);
> +		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
> +	}
> +
> +	addr = drvdata->base + dcc_status(drvdata->mem_map_ver);
> +	if (readl_poll_timeout(addr, val, !FIELD_GET(DCC_STATUS_MASK, val),
> +			       1, STATUS_READY_TIMEOUT)) {
> +		dev_err(drvdata->dev, "DCC is busy after receiving sw trigger\n");
> +		ret = -EBUSY;
> +		goto out_unlock;
> +	}
> +
> +	for (i = 0; i < drvdata->nr_link_list; i++) {
> +		if (!test_bit(i, drvdata->enable_bitmap))
> +			continue;
> +
> +		status = dcc_list_readl(drvdata, i, DCC_LL_BUS_ACCESS_STATUS);
> +		if (!status)
> +			continue;
> +
> +		dev_err(drvdata->dev, "Read access error for list %d err: 0x%x\n",
> +			i, status);
> +		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
> +		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
> +		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
> +		dcc_list_writel(drvdata, DCC_STATUS_MASK, i, DCC_LL_BUS_ACCESS_STATUS);
> +		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
> +		ret = -ENODATA;
> +		break;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +	return ret;
> +}
> +
> +static void dcc_ll_cfg_reset_link(struct dcc_cfg_attr *cfg)
> +{
> +	cfg->addr = 0x00;
> +	cfg->link = 0;
> +	cfg->prev_off = 0;
> +	cfg->prev_addr = cfg->addr;
> +}
> +
> +static void dcc_emit_read_write(struct dcc_drvdata *drvdata,
> +				struct dcc_config_entry *entry,
> +				struct dcc_cfg_attr *cfg)
> +{
> +	if (cfg->link) {
> +		/*
> +		 * write new offset = 1 to continue
> +		 * processing the list
> +		 */
> +
> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +
> +		/* Reset link and prev_off */
> +		dcc_ll_cfg_reset_link(cfg);
> +	}
> +
> +	cfg->addr = DCC_RD_MOD_WR_DESCRIPTOR;
> +	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
> +
> +	dcc_sram_write_auto(drvdata, entry->mask, &cfg->sram_offset);
> +
> +	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
> +
> +	cfg->addr = 0;
> +}
> +
> +static void dcc_emit_loop(struct dcc_drvdata *drvdata, struct dcc_config_entry *entry,
> +			  struct dcc_cfg_attr *cfg,
> +			  struct dcc_cfg_loop_attr *cfg_loop,
> +			  u32 *total_len)
> +{
> +	int loop;
> +
> +	/* Check if we need to write link of prev entry */
> +	if (cfg->link)
> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +
> +	if (cfg_loop->loop_start) {
> +		loop = (cfg->sram_offset - cfg_loop->loop_off) / 4;
> +		loop |= (cfg_loop->loop_cnt << drvdata->loop_shift) &
> +				   GENMASK(DCC_ADDR_LIMIT, drvdata->loop_shift);
> +		loop |= DCC_LOOP_DESCRIPTOR;
> +		*total_len += (*total_len - cfg_loop->loop_len) * cfg_loop->loop_cnt;
> +
> +		dcc_sram_write_auto(drvdata, loop, &cfg->sram_offset);
> +
> +		cfg_loop->loop_start = false;
> +		cfg_loop->loop_len = 0;
> +		cfg_loop->loop_off = 0;
> +	} else {
> +		cfg_loop->loop_start = true;
> +		cfg_loop->loop_cnt = entry->loop_cnt - 1;
> +		cfg_loop->loop_len = *total_len;
> +		cfg_loop->loop_off = cfg->sram_offset;
> +	}
> +
> +	/* Reset link and prev_off */
> +	dcc_ll_cfg_reset_link(cfg);
> +}
> +
> +static void dcc_emit_write(struct dcc_drvdata *drvdata,
> +			   struct dcc_config_entry *entry,
> +			   struct dcc_cfg_attr *cfg)
> +{
> +	u32 off;
> +
> +	if (cfg->link) {
> +		/*
> +		 * write new offset = 1 to continue
> +		 * processing the list
> +		 */
> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +
> +		/* Reset link and prev_off */
> +		cfg->addr = 0x00;
> +		cfg->prev_off = 0;
> +		cfg->prev_addr = cfg->addr;
> +	}
> +
> +	off = entry->offset / 4;
> +	/* write new offset-length pair to correct position */
> +	cfg->link |= ((off & DCC_WRITE_OFF_MASK) | DCC_WRITE_MASK |
> +		      FIELD_PREP(DCC_WRITE_LEN_MASK, entry->len));
> +	cfg->link |= DCC_LINK_DESCRIPTOR;
> +
> +	/* Address type */
> +	cfg->addr = (entry->base >> 4) & GENMASK(DCC_ADDR_LIMIT, 0);
> +	if (entry->apb_bus)
> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_APB_IND;
> +	else
> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_AHB_IND;
> +	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
> +
> +	dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +
> +	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
> +
> +	cfg->addr = 0x00;
> +	cfg->link = 0;
> +}
> +
> +static int dcc_emit_read(struct dcc_drvdata *drvdata,
> +			 struct dcc_config_entry *entry,
> +			 struct dcc_cfg_attr *cfg,
> +			 u32 *pos, u32 *total_len)
> +{
> +	u32 off;
> +	u32 temp_off;
> +
> +	cfg->addr = (entry->base >> 4) & GENMASK(27, 0);
> +
> +	if (entry->apb_bus)
> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_APB_IND;
> +	else
> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_AHB_IND;
> +
> +	off = entry->offset / 4;
> +
> +	*total_len += entry->len * 4;
> +
> +	if (!cfg->prev_addr || cfg->prev_addr != cfg->addr || cfg->prev_off > off) {
> +		/* Check if we need to write prev link entry */
> +		if (cfg->link)
> +			dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +		dev_dbg(drvdata->dev, "DCC: sram address 0x%x\n", cfg->sram_offset);
> +
> +		/* Write address */
> +		dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
> +
> +		/* Reset link and prev_off */
> +		cfg->link = 0;
> +		cfg->prev_off = 0;
> +	}
> +
> +	if ((off - cfg->prev_off) > 0xff || entry->len > MAX_DCC_LEN) {
> +		dev_err(drvdata->dev, "DCC: Programming error Base: 0x%x, offset 0x%x\n",
> +			entry->base, entry->offset);
> +		return -EINVAL;
> +	}
> +
> +	if (cfg->link) {
> +		/*
> +		 * link already has one offset-length so new
> +		 * offset-length needs to be placed at
> +		 * bits [29:15]
> +		 */
> +		*pos = 15;
> +
> +		/* Clear bits [31:16] */
> +		cfg->link &= GENMASK(14, 0);
> +	} else {
> +		/*
> +		 * link is empty, so new offset-length needs
> +		 * to be placed at bits [15:0]
> +		 */
> +		*pos = 0;
> +		cfg->link = 1 << 15;
> +	}
> +
> +	/* write new offset-length pair to correct position */
> +	temp_off = (off - cfg->prev_off) & GENMASK(7, 0);
> +	cfg->link |= temp_off | ((entry->len << 8) & GENMASK(14, 8)) << *pos;
> +
> +	cfg->link |= DCC_LINK_DESCRIPTOR;
> +
> +	if (*pos) {
> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
> +		cfg->link = 0;
> +	}
> +
> +	cfg->prev_off  = off + entry->len - 1;
> +	cfg->prev_addr = cfg->addr;
> +	return 0;
> +}
> +
> +static int dcc_emit_config(struct dcc_drvdata *drvdata, unsigned int curr_list)
> +{
> +	int ret;
> +	u32 total_len, pos;
> +	struct dcc_config_entry *entry;
> +	struct dcc_cfg_attr cfg = {0};
> +	struct dcc_cfg_loop_attr cfg_loop = {0};
> +
> +	cfg.sram_offset = drvdata->ram_cfg * 4;
> +	total_len = 0;
> +
> +	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
> +		switch (entry->desc_type) {
> +		case DCC_READ_WRITE_TYPE:
> +			dcc_emit_read_write(drvdata, entry, &cfg);
> +			break;
> +
> +		case DCC_LOOP_TYPE:
> +			dcc_emit_loop(drvdata, entry, &cfg, &cfg_loop, &total_len);
> +			break;
> +
> +		case DCC_WRITE_TYPE:
> +			dcc_emit_write(drvdata, entry, &cfg);
> +			break;
> +
> +		case DCC_READ_TYPE:
> +			ret = dcc_emit_read(drvdata, entry, &cfg, &pos, &total_len);
> +			if (ret)
> +				goto err;
> +			break;
> +		}
> +	}
> +
> +	if (cfg.link)
> +		dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
> +
> +	if (cfg_loop.loop_start) {
> +		dev_err(drvdata->dev, "DCC: Programming error: Loop unterminated\n");
> +		ret = -EINVAL;
> +		goto err;
> +	}
> +
> +	/* Handling special case of list ending with a rd_mod_wr */
> +	if (cfg.addr == DCC_RD_MOD_WR_DESCRIPTOR) {
> +		cfg.addr = (DCC_RD_MOD_WR_ADDR) & GENMASK(27, 0);
> +		cfg.addr |= DCC_ADDR_DESCRIPTOR;
> +		dcc_sram_write_auto(drvdata, cfg.addr, &cfg.sram_offset);
> +	}
> +
> +	/* Setting zero to indicate end of the list */
> +	cfg.link = DCC_LINK_DESCRIPTOR;
> +	dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
> +
> +	/* Check if sram offset exceeds the ram size */
> +	if (cfg.sram_offset > drvdata->ram_size)
> +		goto overstep;
> +
> +	/* Update ram_cfg and check if the data will overstep */
> +	drvdata->ram_cfg = (cfg.sram_offset + total_len) / 4;
> +
> +	if (cfg.sram_offset + total_len > drvdata->ram_size) {
> +		cfg.sram_offset += total_len;
> +		goto overstep;
> +	}
> +
> +	drvdata->ram_start = cfg.sram_offset / 4;
> +	return 0;
> +overstep:
> +	ret = -EINVAL;
> +	memset_io(drvdata->ram_base, 0, drvdata->ram_size);
> +
> +err:
> +	return ret;
> +}
> +
> +static bool dcc_valid_list(struct dcc_drvdata *drvdata, unsigned int curr_list)
> +{
> +	u32 lock_reg;
> +
> +	if (list_empty(&drvdata->cfg_head[curr_list]))
> +		return false;
> +
> +	if (test_bit(curr_list, drvdata->enable_bitmap)) {
> +		dev_err(drvdata->dev, "List %d is already enabled\n", curr_list);
> +		return false;
> +	}
> +
> +	lock_reg = dcc_list_readl(drvdata, curr_list, DCC_LL_LOCK);
> +	if (lock_reg & DCC_LOCK_MASK) {
> +		dev_err(drvdata->dev, "List %d is already locked\n", curr_list);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static bool is_dcc_enabled(struct dcc_drvdata *drvdata)
> +{
> +	int list;
> +
> +	for (list = 0; list < drvdata->nr_link_list; list++)
> +		if (test_bit(list, drvdata->enable_bitmap))
> +			return true;
> +
> +	return false;
> +}
> +
> +static int dcc_enable(struct dcc_drvdata *drvdata, unsigned int curr_list)
> +{
> +	int ret;
> +	u32 ram_cfg_base;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (!dcc_valid_list(drvdata, curr_list)) {
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	/* Fill dcc sram with the poison value.
> +	 * This helps in understanding bus
> +	 * hang from registers returning a zero
> +	 */
> +	if (!is_dcc_enabled(drvdata))
> +		memset_io(drvdata->ram_base, 0xde, drvdata->ram_size);
> +
> +	/* 1. Take ownership of the list */
> +	dcc_list_writel(drvdata, DCC_LOCK_MASK, curr_list, DCC_LL_LOCK);
> +
> +	/* 2. Program linked-list in the SRAM */
> +	ram_cfg_base = drvdata->ram_cfg;
> +	ret = dcc_emit_config(drvdata, curr_list);
> +	if (ret) {
> +		dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
> +		goto out_unlock;
> +	}
> +
> +	/* 3. Program DCC_RAM_CFG reg */
> +	dcc_list_writel(drvdata, ram_cfg_base +
> +			drvdata->ram_offset / 4, curr_list, DCC_LL_BASE);
> +	dcc_list_writel(drvdata, drvdata->ram_start +
> +			drvdata->ram_offset / 4, curr_list, DCC_FD_BASE);
> +	dcc_list_writel(drvdata, 0xFFF, curr_list, DCC_LL_TIMEOUT);
> +
> +	/* 4. Clears interrupt status register */
> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_INT_ENABLE);
> +	dcc_list_writel(drvdata, (BIT(0) | BIT(1) | BIT(2)),
> +			curr_list, DCC_LL_INT_STATUS);
> +
> +	set_bit(curr_list, drvdata->enable_bitmap);
> +
> +	/* 5. Configure trigger */
> +	dcc_list_writel(drvdata, DCC_TRIGGER_MASK,
> +			curr_list, DCC_LL_CFG);
> +
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +	return ret;
> +}
> +
> +static void dcc_disable(struct dcc_drvdata *drvdata, int curr_list)
> +{
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (!test_bit(curr_list, drvdata->enable_bitmap))
> +		goto out_unlock;
> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_CFG);
> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_BASE);
> +	dcc_list_writel(drvdata, 0, curr_list, DCC_FD_BASE);
> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
> +	clear_bit(curr_list, drvdata->enable_bitmap);
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +}
> +
> +static u32 dcc_filp_curr_list(const struct file *filp)
> +{
> +	struct dentry *dentry = file_dentry(filp);
> +	int curr_list, ret;
> +
> +	ret = kstrtoint(dentry->d_parent->d_name.name, 0, &curr_list);
> +	if (ret)
> +		return ret;
> +
> +	return curr_list;
> +}
> +
> +static ssize_t enable_read(struct file *filp, char __user *userbuf,
> +			   size_t count, loff_t *ppos)
> +{
> +	char *buf;
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (is_dcc_enabled(drvdata))
> +		buf = "Y\n";
> +	else
> +		buf = "N\n";
> +
> +	mutex_unlock(&drvdata->mutex);
> +
> +	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
> +}
> +
> +static ssize_t enable_write(struct file *filp, const char __user *userbuf,
> +			    size_t count, loff_t *ppos)
> +{
> +	int ret = 0, curr_list;
> +	bool val;
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	curr_list = dcc_filp_curr_list(filp);
> +	if (curr_list < 0)
> +		return curr_list;
> +
> +	ret = kstrtobool_from_user(userbuf, count, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (val) {
> +		ret = dcc_enable(drvdata, curr_list);
> +		if (ret)
> +			return ret;
> +	} else {
> +		dcc_disable(drvdata, curr_list);
> +	}
> +
> +	return count;
> +}
> +
> +static const struct file_operations enable_fops = {
> +	.read = enable_read,
> +	.write = enable_write,
> +	.open = simple_open,
> +	.llseek = generic_file_llseek,
> +};
> +
> +static ssize_t trigger_write(struct file *filp,
> +			     const char __user *user_buf, size_t count,
> +			     loff_t *ppos)
> +{
> +	int ret;
> +	unsigned int val;
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	ret = kstrtouint_from_user(user_buf, count, 0, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (val != 1)
> +		return -EINVAL;
> +
> +	ret = dcc_sw_trigger(drvdata);
> +	if (ret < 0)
> +		return ret;
> +
> +	return count;
> +}
> +
> +static const struct file_operations trigger_fops = {
> +	.write = trigger_write,
> +	.open = simple_open,
> +	.llseek = generic_file_llseek,
> +};
> +
> +static int dcc_config_add(struct dcc_drvdata *drvdata, unsigned int addr,
> +			  unsigned int len, bool apb_bus, int curr_list)
> +{
> +	int ret = 0;
> +	struct dcc_config_entry *entry, *pentry;
> +	unsigned int base, offset;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (!len || len > drvdata->ram_size / DCC_WORD_SIZE) {
> +		dev_err(drvdata->dev, "DCC: Invalid length\n");
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	base = addr & DCC_ADDR_RANGE_MASK;
> +
> +	if (!list_empty(&drvdata->cfg_head[curr_list])) {
> +		pentry = list_last_entry(&drvdata->cfg_head[curr_list],
> +					 struct dcc_config_entry, list);
> +
> +		if (pentry->desc_type == DCC_READ_TYPE &&
> +		    addr >= (pentry->base + pentry->offset) &&
> +		    addr <= (pentry->base + pentry->offset + MAX_DCC_OFFSET)) {
> +			/* Re-use base address from last entry */
> +			base = pentry->base;
> +
> +			if ((pentry->len * 4 + pentry->base + pentry->offset)
> +					== addr) {
> +				len += pentry->len;
> +
> +				if (len > MAX_DCC_LEN)
> +					pentry->len = MAX_DCC_LEN;
> +				else
> +					pentry->len = len;
> +
> +				addr = pentry->base + pentry->offset +
> +					pentry->len * 4;
> +				len -= pentry->len;
> +			}
> +		}
> +	}
> +
> +	offset = addr - base;
> +
> +	while (len) {
> +		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> +		if (!entry) {
> +			ret = -ENOMEM;
> +			goto out_unlock;
> +		}
> +
> +		entry->base = base;
> +		entry->offset = offset;
> +		entry->len = min_t(u32, len, MAX_DCC_LEN);
> +		entry->desc_type = DCC_READ_TYPE;
> +		entry->apb_bus = apb_bus;
> +		INIT_LIST_HEAD(&entry->list);
> +		list_add_tail(&entry->list,
> +			      &drvdata->cfg_head[curr_list]);
> +
> +		len -= entry->len;
> +		offset += MAX_DCC_LEN * 4;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +	return ret;
> +}
> +
> +static ssize_t dcc_config_add_read(struct dcc_drvdata *drvdata, char *buf, int curr_list)
> +{
> +	bool bus;
> +	int len, nval;
> +	unsigned int base;
> +	char apb_bus[4];
> +
> +	nval = sscanf(buf, "%x %i %3s", &base, &len, apb_bus);
> +	if (nval <= 0 || nval > 3)
> +		return -EINVAL;
> +
> +	if (nval == 1) {
> +		len = 1;
> +		bus = false;
> +	} else if (nval == 2) {
> +		bus = false;
> +	} else if (!strcmp("apb", apb_bus)) {
> +		bus = true;
> +	} else if (!strcmp("ahb", apb_bus)) {
> +		bus = false;
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	return dcc_config_add(drvdata, base, len, bus, curr_list);
> +}
> +
> +static void dcc_config_reset(struct dcc_drvdata *drvdata)
> +{
> +	struct dcc_config_entry *entry, *temp;
> +	int curr_list;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
> +		list_for_each_entry_safe(entry, temp,
> +					 &drvdata->cfg_head[curr_list], list) {
> +			list_del(&entry->list);
> +			kfree(entry);
> +		}
> +	}
> +	drvdata->ram_start = 0;
> +	drvdata->ram_cfg = 0;
> +	mutex_unlock(&drvdata->mutex);
> +}
> +
> +static ssize_t config_reset_write(struct file *filp,
> +				  const char __user *user_buf, size_t count,
> +				  loff_t *ppos)
> +{
> +	unsigned int val, ret;
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	ret = kstrtouint_from_user(user_buf, count, 0, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (val)
> +		dcc_config_reset(drvdata);
> +
> +	return count;
> +}
> +
> +static const struct file_operations config_reset_fops = {
> +	.write = config_reset_write,
> +	.open = simple_open,
> +	.llseek = generic_file_llseek,
> +};
> +
> +static ssize_t ready_read(struct file *filp, char __user *userbuf,
> +			  size_t count, loff_t *ppos)
> +{
> +	int ret = 0;
> +	char *buf;
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (!is_dcc_enabled(drvdata)) {
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
> +		buf = "Y\n";
> +	else
> +		buf = "N\n";
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +
> +	if (ret < 0)
> +		return -EINVAL;
> +	else

You do the "lock, get a value, unlock, do something with the value"
thing a bunch, but what prevents the value from changing after the lock
happens?  So why is the lock needed at all?

thanks,

greg k-h

> +		return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf) + 1);
> +}
> +
> +static const struct file_operations ready_fops = {
> +	.read = ready_read,
> +	.open = simple_open,
> +	.llseek = generic_file_llseek,
> +};
> +
> +static int dcc_add_loop(struct dcc_drvdata *drvdata, unsigned long loop_cnt, int curr_list)
> +{
> +	struct dcc_config_entry *entry;
> +
> +	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> +	if (!entry)
> +		return -ENOMEM;
> +
> +	entry->loop_cnt = min_t(u32, loop_cnt, MAX_LOOP_CNT);
> +	entry->desc_type = DCC_LOOP_TYPE;
> +	INIT_LIST_HEAD(&entry->list);
> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
> +
> +	return 0;
> +}
> +
> +static ssize_t dcc_config_add_loop(struct dcc_drvdata *drvdata, char *buf, int curr_list)
> +{
> +	int ret, i = 0;
> +	char *token, *input;
> +	char delim[2] = " ";
> +	unsigned int val[MAX_LOOP_ADDR];
> +
> +	input = buf;
> +
> +	while ((token = strsep(&input, delim)) && i < MAX_LOOP_ADDR) {
> +		ret = kstrtoint(token, 0, &val[i++]);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (token) {
> +		dev_err(drvdata->dev, "Max limit %u of loop address exceeded",
> +			MAX_LOOP_ADDR);
> +		return -EINVAL;
> +	}
> +
> +	if (val[1] < 1 || val[1] > 8)
> +		return -EINVAL;
> +
> +	ret = dcc_add_loop(drvdata, val[0], curr_list);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < val[1]; i++)
> +		dcc_config_add(drvdata, val[i + 2], 1, false, curr_list);
> +
> +	return dcc_add_loop(drvdata, 1, curr_list);
> +}
> +
> +static int dcc_rd_mod_wr_add(struct dcc_drvdata *drvdata, unsigned int mask,
> +			     unsigned int val, int curr_list)
> +{
> +	int ret = 0;
> +	struct dcc_config_entry *entry;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	if (list_empty(&drvdata->cfg_head[curr_list])) {
> +		dev_err(drvdata->dev, "DCC: No read address programmed\n");
> +		ret = -EPERM;
> +		goto out_unlock;
> +	}
> +
> +	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> +	if (!entry) {
> +		ret = -ENOMEM;
> +		goto out_unlock;
> +	}
> +
> +	entry->desc_type = DCC_READ_WRITE_TYPE;
> +	entry->mask = mask;
> +	entry->write_val = val;
> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
> +out_unlock:
> +	mutex_unlock(&drvdata->mutex);
> +	return ret;
> +}
> +
> +static ssize_t dcc_config_add_read_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
> +{
> +	int ret;
> +	int nval;
> +	unsigned int addr, mask, val;
> +
> +	nval = sscanf(buf, "%x %x %x", &addr, &mask, &val);
> +
> +	if (nval <= 1 || nval > 3)
> +		return -EINVAL;
> +
> +	ret = dcc_config_add(drvdata, addr, 1, false, curr_list);
> +	if (ret)
> +		return ret;
> +
> +	return dcc_rd_mod_wr_add(drvdata, mask, val, curr_list);
> +}
> +
> +static int dcc_add_write(struct dcc_drvdata *drvdata, unsigned int addr,
> +			 unsigned int write_val, int apb_bus, int curr_list)
> +{
> +	struct dcc_config_entry *entry;
> +
> +	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> +	if (!entry)
> +		return -ENOMEM;
> +
> +	entry->desc_type = DCC_WRITE_TYPE;
> +	entry->base = addr & GENMASK(31, 4);
> +	entry->offset = addr - entry->base;
> +	entry->write_val = write_val;
> +	entry->len = 1;
> +	entry->apb_bus = apb_bus;
> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
> +
> +	return 0;
> +}
> +
> +static ssize_t dcc_config_add_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
> +{
> +	bool bus;
> +	int nval;
> +	unsigned int addr, write_val;
> +	char apb_bus[4];
> +
> +	nval = sscanf(buf, "%x %x %3s", &addr, &write_val, apb_bus);
> +
> +	if (nval <= 1 || nval > 3)
> +		return -EINVAL;
> +
> +	if (nval == 2)
> +		bus = true;
> +
> +	if (nval == 3) {
> +		if (!strcmp("apb", apb_bus))
> +			bus = true;
> +		else if (!strcmp("ahb", apb_bus))
> +			bus = false;
> +		else
> +			return -EINVAL;
> +	}
> +
> +	return dcc_add_write(drvdata, addr, write_val, bus, curr_list);
> +}
> +
> +static int config_show(struct seq_file *m, void *data)
> +{
> +	struct dcc_drvdata *drvdata = m->private;
> +	struct dcc_config_entry *entry;
> +	int index = 0, curr_list;
> +
> +	curr_list = dcc_filp_curr_list(m->file);
> +	if (curr_list < 0)
> +		return curr_list;
> +
> +	mutex_lock(&drvdata->mutex);
> +
> +	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
> +		index++;
> +		switch (entry->desc_type) {
> +		case DCC_READ_WRITE_TYPE:
> +			seq_printf(m, "RW mask: 0x%x, val: 0x%x\n index: 0x%x\n",
> +				   entry->mask, entry->write_val, index);
> +			break;
> +		case DCC_LOOP_TYPE:
> +			seq_printf(m, "L index: 0x%x Loop: %d\n", index, entry->loop_cnt);
> +			break;
> +		case DCC_WRITE_TYPE:
> +			seq_printf(m, "W Base:0x%x, Offset: 0x%x, val: 0x%x, APB: %d\n, Index: 0x%x\n",
> +				   entry->base, entry->offset, entry->write_val, entry->apb_bus,
> +				   index);
> +			break;
> +		case DCC_READ_TYPE:
> +			seq_printf(m, "R Base:0x%x, Offset: 0x%x, len: 0x%x, APB: %d\n, Index: 0x%x\n",
> +				   entry->base, entry->offset, entry->len, entry->apb_bus, index);
> +		}
> +	}
> +	mutex_unlock(&drvdata->mutex);
> +	return 0;
> +}
> +
> +static int config_open(struct inode *inode, struct file *file)
> +{
> +	struct dcc_drvdata *drvdata = inode->i_private;
> +
> +	return single_open(file, config_show, drvdata);
> +}
> +
> +static ssize_t config_write(struct file *filp,
> +			    const char __user *user_buf, size_t count,
> +			    loff_t *ppos)
> +{
> +	int ret, curr_list;
> +	char *token, buf[50];
> +	char *bufp = buf;
> +	char *delim = " ";
> +	struct dcc_drvdata *drvdata = filp->private_data;
> +
> +	if (count > sizeof(buf) || count == 0)
> +		return -EINVAL;
> +
> +	ret = copy_from_user(buf, user_buf, count);
> +	if (ret)
> +		return -EFAULT;
> +
> +	curr_list = dcc_filp_curr_list(filp);
> +	if (curr_list < 0)
> +		return curr_list;
> +
> +	if (buf[count - 1] == '\n')
> +		buf[count - 1] = '\0';
> +	else
> +		return -EINVAL;
> +
> +	token = strsep(&bufp, delim);
> +
> +	if (!strcmp("R", token)) {
> +		ret = dcc_config_add_read(drvdata, bufp, curr_list);
> +	} else if (!strcmp("W", token)) {
> +		ret = dcc_config_add_write(drvdata, bufp, curr_list);
> +	} else if (!strcmp("RW", token)) {
> +		ret = dcc_config_add_read_write(drvdata, bufp, curr_list);
> +	} else if (!strcmp("L", token)) {
> +		ret = dcc_config_add_loop(drvdata, bufp, curr_list);
> +	} else {
> +		dev_err(drvdata->dev, "%s is not a correct input\n", token);
> +		return -EINVAL;
> +	}
> +
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +static const struct file_operations config_fops = {
> +	.open = config_open,
> +	.read = seq_read,
> +	.write = config_write,
> +	.llseek = seq_lseek,
> +	.release = single_release,
> +};
> +
> +static void dcc_delete_debug_dir(struct dcc_drvdata *drvdata)
> +{
> +	 debugfs_remove_recursive(drvdata->dbg_dir);
> +};
> +
> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
> +{
> +	int i;
> +	char list_num[10];
> +	struct dentry *dcc_dev, *list;
> +	struct device *dev = drvdata->dev;
> +
> +	drvdata->dbg_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
> +	dcc_dev = debugfs_create_dir(dev_name(dev), drvdata->dbg_dir);
> +
> +	for (i = 0; i <= drvdata->nr_link_list; i++) {
> +		sprintf(list_num, "%d", i);
> +		list = debugfs_create_dir(list_num, dcc_dev);
> +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
> +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
> +	}
> +
> +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
> +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
> +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
> +			    drvdata, &config_reset_fops);
> +}
> +
> +static ssize_t dcc_sram_read(struct file *file, char __user *data,
> +			     size_t len, loff_t *ppos)
> +{
> +	unsigned char *buf;
> +	struct dcc_drvdata *drvdata;
> +
> +	drvdata = container_of(file->private_data, struct dcc_drvdata,
> +			       sram_dev);
> +
> +	/* EOF check */
> +	if (*ppos >= drvdata->ram_size)
> +		return 0;
> +
> +	if ((*ppos + len) > drvdata->ram_size)
> +		len = (drvdata->ram_size - *ppos);
> +
> +	buf = kzalloc(len, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	memcpy_fromio(buf, drvdata->ram_base + *ppos, len);
> +
> +	if (copy_to_user(data, buf, len)) {
> +		kfree(buf);
> +		return -EFAULT;
> +	}
> +
> +	*ppos += len;
> +
> +	kfree(buf);
> +
> +	return len;
> +}
> +
> +static const struct file_operations dcc_sram_fops = {
> +	.owner		= THIS_MODULE,
> +	.read		= dcc_sram_read,
> +	.llseek		= no_llseek,
> +};
> +
> +static int dcc_sram_dev_init(struct dcc_drvdata *drvdata)
> +{
> +	drvdata->sram_dev.minor = MISC_DYNAMIC_MINOR;
> +	drvdata->sram_dev.name = "dcc_sram";
> +	drvdata->sram_dev.fops = &dcc_sram_fops;
> +
> +	return misc_register(&drvdata->sram_dev);
> +}
> +
> +static void dcc_sram_dev_exit(struct dcc_drvdata *drvdata)
> +{
> +	misc_deregister(&drvdata->sram_dev);
> +}
> +
> +static int dcc_probe(struct platform_device *pdev)
> +{
> +	u32 val;
> +	int ret = 0, i;
> +	struct device *dev = &pdev->dev;
> +	struct dcc_drvdata *drvdata;
> +	struct resource *res;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->dev = &pdev->dev;
> +	platform_set_drvdata(pdev, drvdata);
> +
> +	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(drvdata->base))
> +		return PTR_ERR(drvdata->base);
> +
> +	drvdata->ram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
> +	if (IS_ERR(drvdata->ram_base))
> +		return PTR_ERR(drvdata->ram_base);
> +
> +	drvdata->ram_size = resource_size(res);
> +
> +	drvdata->ram_offset = (size_t)of_device_get_match_data(&pdev->dev);
> +
> +	val = readl(drvdata->base + DCC_HW_INFO);
> +
> +	if (FIELD_GET(DCC_VER_INFO_MASK, val)) {
> +		drvdata->mem_map_ver = 3;
> +		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
> +		if (!drvdata->nr_link_list)
> +			return	-EINVAL;
> +	} else if ((val & DCC_VER_MASK2) == DCC_VER_MASK2) {
> +		drvdata->mem_map_ver = 2;
> +		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
> +		if (!drvdata->nr_link_list)
> +			return	-EINVAL;
> +	} else {
> +		drvdata->mem_map_ver = 1;
> +		drvdata->nr_link_list = DCC_MAX_LINK_LIST;
> +	}
> +
> +	/* Either set the fixed loop offset or calculate
> +	 * it from the total number of words in dcc_sram.
> +	 * Max consecutive addresses dcc can loop is
> +	 * equivalent to the words in dcc_sram.
> +	 */
> +	if (val & DCC_LOOP_OFFSET_MASK)
> +		drvdata->loop_shift = DCC_FIX_LOOP_OFFSET;
> +	else
> +		drvdata->loop_shift = get_bitmask_order((drvdata->ram_offset +
> +					drvdata->ram_size) / DCC_SRAM_WORD_LENGTH - 1);
> +
> +	mutex_init(&drvdata->mutex);
> +
> +	drvdata->enable_bitmap = devm_kcalloc(dev, BITS_TO_LONGS(drvdata->nr_link_list),
> +					      sizeof(*drvdata->enable_bitmap), GFP_KERNEL);
> +	if (!drvdata->enable_bitmap)
> +		return -ENOMEM;
> +
> +	drvdata->cfg_head = devm_kcalloc(dev, drvdata->nr_link_list,
> +					 sizeof(*drvdata->cfg_head), GFP_KERNEL);
> +	if (!drvdata->cfg_head)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < drvdata->nr_link_list; i++)
> +		INIT_LIST_HEAD(&drvdata->cfg_head[i]);
> +
> +	ret = dcc_sram_dev_init(drvdata);
> +	if (ret) {
> +		dev_err(drvdata->dev, "DCC: sram node not registered.\n");
> +		return ret;
> +	}
> +
> +	dcc_create_debug_dir(drvdata);
> +
> +	return 0;
> +}
> +
> +static int dcc_remove(struct platform_device *pdev)
> +{
> +	struct dcc_drvdata *drvdata = platform_get_drvdata(pdev);
> +
> +	dcc_delete_debug_dir(drvdata);
> +	dcc_sram_dev_exit(drvdata);
> +	dcc_config_reset(drvdata);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id dcc_match_table[] = {
> +	{ .compatible = "qcom,sc7180-dcc", .data = (void *)0x6000 },
> +	{ .compatible = "qcom,sc7280-dcc", .data = (void *)0x12000 },
> +	{ .compatible = "qcom,sdm845-dcc", .data = (void *)0x6000 },
> +	{ .compatible = "qcom,sm8150-dcc", .data = (void *)0x5000 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, dcc_match_table);
> +
> +static struct platform_driver dcc_driver = {
> +	.probe = dcc_probe,
> +	.remove	= dcc_remove,
> +	.driver	= {
> +		.name = "qcom-dcc",
> +		.of_match_table	= dcc_match_table,
> +	},
> +};
> +
> +module_platform_driver(dcc_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Qualcomm Technologies Inc. DCC driver");
> +
> -- 
> 2.17.1
>

Souradeep Chowdhury June 15, 2023, 12:43 p.m. UTC | #4

On 6/15/2023 4:03 PM, Greg Kroah-Hartman wrote:
> On Thu, May 04, 2023 at 11:36:22PM -0700, Souradeep Chowdhury wrote:
>> +/**
>> + * struct dcc_config_entry - configuration information related to each dcc instruction
>> + * @base:                    Base address of the register to be configured in dcc
> 
> Why is this a u32 and not a bigger size?

Currently only 32 bit register addresses are supported for DCC 
configuration.

> 
>> + * @offset:                  Offset to the base address to be configured in dcc
>> + * @len:                     Length of the address in words to be configured in dcc
> 
> What is a "word" here, 16 bits?

Each word is 4 bytes(32 bits)

> 
>> + * @loop_cnt:                The number of times to loop on the register address in case
>> +				of loop instructions
>> + * @write_val:               The value to be written on the register address in case of
>> +				write instructions
>> + * @mask:                    Mask corresponding to the value to be written in case of
>> +				write instructions
>> + * @apb_bus:                 Type of bus to be used for the instruction, can be either
>> +				'apb' or 'ahb'
> 
> How can a bool be either "apb" or "ahb"?

1 stands for apb and 0 for ahb. Will update the same here.

> 
>> + * @desc_type:               Stores the type of dcc instruction
>> + * @list:                    This is used to append this instruction to the list of
>> +				instructions
>> + */
>> +struct dcc_config_entry {
>> +	u32				base;
>> +	u32				offset;
>> +	u32				len;
>> +	u32				loop_cnt;
>> +	u32				write_val;
>> +	u32				mask;
>> +	bool				apb_bus;
>> +	enum dcc_descriptor_type	desc_type;
>> +	struct list_head		list;
>> +};
>> +
>> +/**
>> + * struct dcc_drvdata - configuration information related to a dcc device
>> + * @base:		Base Address of the dcc device
>> + * @dev:		The device attached to the driver data
>> + * @mutex:		Lock to protect access and manipulation of dcc_drvdata
>> + * @ram_base:		Base address for the SRAM dedicated for the dcc device
>> + * @ram_size:		Total size of the SRAM dedicated for the dcc device
>> + * @ram_offset:		Offset to the SRAM dedicated for dcc device
>> + * @mem_map_ver:	Memory map version of DCC hardware
>> + * @ram_cfg:		Used for address limit calculation for dcc
>> + * @ram_start:		Starting address of DCC SRAM
>> + * @sram_dev:		Miscellaneous device equivalent of dcc SRAM
>> + * @cfg_head:		Points to the head of the linked list of addresses
>> + * @dbg_dir:		The dcc debugfs directory under which all the debugfs files are placed
>> + * @nr_link_list:	Total number of linkedlists supported by the DCC configuration
>> + * @loop_shift:		Loop offset bits range for the addresses
>> + * @enable_bitmap:	Bitmap to capture the enabled status of each linked list of addresses
> 
> You use a pointer for a bitmap?

Yes because the generic kernel functions on bitmaps test_bit,set_bit 
takes pointer as the argument.

> 
>> + */
>> +struct dcc_drvdata {
>> +	void __iomem		*base;
>> +	void __iomem            *ram_base;
>> +	struct device		*dev;
>> +	struct mutex		mutex;
>> +	size_t			ram_size;
>> +	size_t			ram_offset;
>> +	int			mem_map_ver;
> 
> u64?

Ack

> 
>> +	unsigned int		ram_cfg;
>> +	unsigned int		ram_start;
>> +	struct miscdevice	sram_dev;
>> +	struct list_head	*cfg_head;
>> +	struct dentry		*dbg_dir;
>> +	size_t			nr_link_list;
> 
> "nr"?

Will change this to max_link_list.

> 
>> +	u8			loop_shift;
>> +	unsigned long		*enable_bitmap;
>> +};
>> +
>> +struct dcc_cfg_attr {
>> +	u32	addr;
>> +	u32	prev_addr;
>> +	u32	prev_off;
>> +	u32	link;
>> +	u32	sram_offset;
>> +};
>> +
>> +struct dcc_cfg_loop_attr {
>> +	u32	loop_cnt;
>> +	u32	loop_len;
>> +	u32	loop_off;
>> +	bool    loop_start;
>> +};
>> +
>> +static inline u32 dcc_status(int version)
>> +{
>> +	return version == 1 ? 0x0c : 0x1c;
>> +}
>> +
>> +static inline u32 dcc_list_offset(int version)
>> +{
>> +	if (version == 1)
>> +		return 0x1c;
>> +	else if (version == 2)
>> +		return 0x2c;
>> +	else
>> +		return 0x34;
>> +}
>> +
>> +static inline void dcc_list_writel(struct dcc_drvdata *drvdata,
>> +				   u32 ll, u32 val, u32 off)
>> +{
>> +	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
>> +
>> +	writel(val, drvdata->base + ll * DCC_LL_OFFSET + offset);
>> +}
>> +
>> +static inline u32 dcc_list_readl(struct dcc_drvdata *drvdata, u32 ll, u32 off)
>> +{
>> +	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
>> +
>> +	return readl(drvdata->base + ll * DCC_LL_OFFSET + offset);
>> +}
>> +
>> +static void dcc_sram_write_auto(struct dcc_drvdata *drvdata,
>> +				u32 val, u32 *off)
>> +{
>> +	/* If the overflow condition is met increment the offset
>> +	 * and return to indicate that overflow has occurred
>> +	 */
>> +	if (unlikely(*off > drvdata->ram_size - 4)) {
> 
> If you can not measure the difference in userspace when using
> likely/unlikely, then never use it as the compiler and CPU will do it
> better for you.

Ack

> 
>> +		*off += 4;
>> +		return;
>> +	}
>> +
>> +	writel(val, drvdata->ram_base + *off);
>> +
>> +	*off += 4;
>> +}
>> +
>> +static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
>> +{
>> +	void __iomem *addr;
>> +	int i;
>> +	u32 status;
>> +	u32 ll_cfg;
>> +	u32 tmp_ll_cfg;
>> +	u32 val;
>> +	int ret = 0;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	for (i = 0; i < drvdata->nr_link_list; i++) {
>> +		if (!test_bit(i, drvdata->enable_bitmap))
>> +			continue;
>> +		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
>> +		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
>> +		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
>> +		dcc_list_writel(drvdata, 1, i, DCC_LL_SW_TRIGGER);
>> +		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
>> +	}
>> +
>> +	addr = drvdata->base + dcc_status(drvdata->mem_map_ver);
>> +	if (readl_poll_timeout(addr, val, !FIELD_GET(DCC_STATUS_MASK, val),
>> +			       1, STATUS_READY_TIMEOUT)) {
>> +		dev_err(drvdata->dev, "DCC is busy after receiving sw trigger\n");
>> +		ret = -EBUSY;
>> +		goto out_unlock;
>> +	}
>> +
>> +	for (i = 0; i < drvdata->nr_link_list; i++) {
>> +		if (!test_bit(i, drvdata->enable_bitmap))
>> +			continue;
>> +
>> +		status = dcc_list_readl(drvdata, i, DCC_LL_BUS_ACCESS_STATUS);
>> +		if (!status)
>> +			continue;
>> +
>> +		dev_err(drvdata->dev, "Read access error for list %d err: 0x%x\n",
>> +			i, status);
>> +		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
>> +		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
>> +		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
>> +		dcc_list_writel(drvdata, DCC_STATUS_MASK, i, DCC_LL_BUS_ACCESS_STATUS);
>> +		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
>> +		ret = -ENODATA;
>> +		break;
>> +	}
>> +
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +	return ret;
>> +}
>> +
>> +static void dcc_ll_cfg_reset_link(struct dcc_cfg_attr *cfg)
>> +{
>> +	cfg->addr = 0x00;
>> +	cfg->link = 0;
>> +	cfg->prev_off = 0;
>> +	cfg->prev_addr = cfg->addr;
>> +}
>> +
>> +static void dcc_emit_read_write(struct dcc_drvdata *drvdata,
>> +				struct dcc_config_entry *entry,
>> +				struct dcc_cfg_attr *cfg)
>> +{
>> +	if (cfg->link) {
>> +		/*
>> +		 * write new offset = 1 to continue
>> +		 * processing the list
>> +		 */
>> +
>> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +
>> +		/* Reset link and prev_off */
>> +		dcc_ll_cfg_reset_link(cfg);
>> +	}
>> +
>> +	cfg->addr = DCC_RD_MOD_WR_DESCRIPTOR;
>> +	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
>> +
>> +	dcc_sram_write_auto(drvdata, entry->mask, &cfg->sram_offset);
>> +
>> +	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
>> +
>> +	cfg->addr = 0;
>> +}
>> +
>> +static void dcc_emit_loop(struct dcc_drvdata *drvdata, struct dcc_config_entry *entry,
>> +			  struct dcc_cfg_attr *cfg,
>> +			  struct dcc_cfg_loop_attr *cfg_loop,
>> +			  u32 *total_len)
>> +{
>> +	int loop;
>> +
>> +	/* Check if we need to write link of prev entry */
>> +	if (cfg->link)
>> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +
>> +	if (cfg_loop->loop_start) {
>> +		loop = (cfg->sram_offset - cfg_loop->loop_off) / 4;
>> +		loop |= (cfg_loop->loop_cnt << drvdata->loop_shift) &
>> +				   GENMASK(DCC_ADDR_LIMIT, drvdata->loop_shift);
>> +		loop |= DCC_LOOP_DESCRIPTOR;
>> +		*total_len += (*total_len - cfg_loop->loop_len) * cfg_loop->loop_cnt;
>> +
>> +		dcc_sram_write_auto(drvdata, loop, &cfg->sram_offset);
>> +
>> +		cfg_loop->loop_start = false;
>> +		cfg_loop->loop_len = 0;
>> +		cfg_loop->loop_off = 0;
>> +	} else {
>> +		cfg_loop->loop_start = true;
>> +		cfg_loop->loop_cnt = entry->loop_cnt - 1;
>> +		cfg_loop->loop_len = *total_len;
>> +		cfg_loop->loop_off = cfg->sram_offset;
>> +	}
>> +
>> +	/* Reset link and prev_off */
>> +	dcc_ll_cfg_reset_link(cfg);
>> +}
>> +
>> +static void dcc_emit_write(struct dcc_drvdata *drvdata,
>> +			   struct dcc_config_entry *entry,
>> +			   struct dcc_cfg_attr *cfg)
>> +{
>> +	u32 off;
>> +
>> +	if (cfg->link) {
>> +		/*
>> +		 * write new offset = 1 to continue
>> +		 * processing the list
>> +		 */
>> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +
>> +		/* Reset link and prev_off */
>> +		cfg->addr = 0x00;
>> +		cfg->prev_off = 0;
>> +		cfg->prev_addr = cfg->addr;
>> +	}
>> +
>> +	off = entry->offset / 4;
>> +	/* write new offset-length pair to correct position */
>> +	cfg->link |= ((off & DCC_WRITE_OFF_MASK) | DCC_WRITE_MASK |
>> +		      FIELD_PREP(DCC_WRITE_LEN_MASK, entry->len));
>> +	cfg->link |= DCC_LINK_DESCRIPTOR;
>> +
>> +	/* Address type */
>> +	cfg->addr = (entry->base >> 4) & GENMASK(DCC_ADDR_LIMIT, 0);
>> +	if (entry->apb_bus)
>> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_APB_IND;
>> +	else
>> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_AHB_IND;
>> +	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
>> +
>> +	dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +
>> +	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
>> +
>> +	cfg->addr = 0x00;
>> +	cfg->link = 0;
>> +}
>> +
>> +static int dcc_emit_read(struct dcc_drvdata *drvdata,
>> +			 struct dcc_config_entry *entry,
>> +			 struct dcc_cfg_attr *cfg,
>> +			 u32 *pos, u32 *total_len)
>> +{
>> +	u32 off;
>> +	u32 temp_off;
>> +
>> +	cfg->addr = (entry->base >> 4) & GENMASK(27, 0);
>> +
>> +	if (entry->apb_bus)
>> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_APB_IND;
>> +	else
>> +		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_AHB_IND;
>> +
>> +	off = entry->offset / 4;
>> +
>> +	*total_len += entry->len * 4;
>> +
>> +	if (!cfg->prev_addr || cfg->prev_addr != cfg->addr || cfg->prev_off > off) {
>> +		/* Check if we need to write prev link entry */
>> +		if (cfg->link)
>> +			dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +		dev_dbg(drvdata->dev, "DCC: sram address 0x%x\n", cfg->sram_offset);
>> +
>> +		/* Write address */
>> +		dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
>> +
>> +		/* Reset link and prev_off */
>> +		cfg->link = 0;
>> +		cfg->prev_off = 0;
>> +	}
>> +
>> +	if ((off - cfg->prev_off) > 0xff || entry->len > MAX_DCC_LEN) {
>> +		dev_err(drvdata->dev, "DCC: Programming error Base: 0x%x, offset 0x%x\n",
>> +			entry->base, entry->offset);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (cfg->link) {
>> +		/*
>> +		 * link already has one offset-length so new
>> +		 * offset-length needs to be placed at
>> +		 * bits [29:15]
>> +		 */
>> +		*pos = 15;
>> +
>> +		/* Clear bits [31:16] */
>> +		cfg->link &= GENMASK(14, 0);
>> +	} else {
>> +		/*
>> +		 * link is empty, so new offset-length needs
>> +		 * to be placed at bits [15:0]
>> +		 */
>> +		*pos = 0;
>> +		cfg->link = 1 << 15;
>> +	}
>> +
>> +	/* write new offset-length pair to correct position */
>> +	temp_off = (off - cfg->prev_off) & GENMASK(7, 0);
>> +	cfg->link |= temp_off | ((entry->len << 8) & GENMASK(14, 8)) << *pos;
>> +
>> +	cfg->link |= DCC_LINK_DESCRIPTOR;
>> +
>> +	if (*pos) {
>> +		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
>> +		cfg->link = 0;
>> +	}
>> +
>> +	cfg->prev_off  = off + entry->len - 1;
>> +	cfg->prev_addr = cfg->addr;
>> +	return 0;
>> +}
>> +
>> +static int dcc_emit_config(struct dcc_drvdata *drvdata, unsigned int curr_list)
>> +{
>> +	int ret;
>> +	u32 total_len, pos;
>> +	struct dcc_config_entry *entry;
>> +	struct dcc_cfg_attr cfg = {0};
>> +	struct dcc_cfg_loop_attr cfg_loop = {0};
>> +
>> +	cfg.sram_offset = drvdata->ram_cfg * 4;
>> +	total_len = 0;
>> +
>> +	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
>> +		switch (entry->desc_type) {
>> +		case DCC_READ_WRITE_TYPE:
>> +			dcc_emit_read_write(drvdata, entry, &cfg);
>> +			break;
>> +
>> +		case DCC_LOOP_TYPE:
>> +			dcc_emit_loop(drvdata, entry, &cfg, &cfg_loop, &total_len);
>> +			break;
>> +
>> +		case DCC_WRITE_TYPE:
>> +			dcc_emit_write(drvdata, entry, &cfg);
>> +			break;
>> +
>> +		case DCC_READ_TYPE:
>> +			ret = dcc_emit_read(drvdata, entry, &cfg, &pos, &total_len);
>> +			if (ret)
>> +				goto err;
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (cfg.link)
>> +		dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
>> +
>> +	if (cfg_loop.loop_start) {
>> +		dev_err(drvdata->dev, "DCC: Programming error: Loop unterminated\n");
>> +		ret = -EINVAL;
>> +		goto err;
>> +	}
>> +
>> +	/* Handling special case of list ending with a rd_mod_wr */
>> +	if (cfg.addr == DCC_RD_MOD_WR_DESCRIPTOR) {
>> +		cfg.addr = (DCC_RD_MOD_WR_ADDR) & GENMASK(27, 0);
>> +		cfg.addr |= DCC_ADDR_DESCRIPTOR;
>> +		dcc_sram_write_auto(drvdata, cfg.addr, &cfg.sram_offset);
>> +	}
>> +
>> +	/* Setting zero to indicate end of the list */
>> +	cfg.link = DCC_LINK_DESCRIPTOR;
>> +	dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
>> +
>> +	/* Check if sram offset exceeds the ram size */
>> +	if (cfg.sram_offset > drvdata->ram_size)
>> +		goto overstep;
>> +
>> +	/* Update ram_cfg and check if the data will overstep */
>> +	drvdata->ram_cfg = (cfg.sram_offset + total_len) / 4;
>> +
>> +	if (cfg.sram_offset + total_len > drvdata->ram_size) {
>> +		cfg.sram_offset += total_len;
>> +		goto overstep;
>> +	}
>> +
>> +	drvdata->ram_start = cfg.sram_offset / 4;
>> +	return 0;
>> +overstep:
>> +	ret = -EINVAL;
>> +	memset_io(drvdata->ram_base, 0, drvdata->ram_size);
>> +
>> +err:
>> +	return ret;
>> +}
>> +
>> +static bool dcc_valid_list(struct dcc_drvdata *drvdata, unsigned int curr_list)
>> +{
>> +	u32 lock_reg;
>> +
>> +	if (list_empty(&drvdata->cfg_head[curr_list]))
>> +		return false;
>> +
>> +	if (test_bit(curr_list, drvdata->enable_bitmap)) {
>> +		dev_err(drvdata->dev, "List %d is already enabled\n", curr_list);
>> +		return false;
>> +	}
>> +
>> +	lock_reg = dcc_list_readl(drvdata, curr_list, DCC_LL_LOCK);
>> +	if (lock_reg & DCC_LOCK_MASK) {
>> +		dev_err(drvdata->dev, "List %d is already locked\n", curr_list);
>> +		return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>> +static bool is_dcc_enabled(struct dcc_drvdata *drvdata)
>> +{
>> +	int list;
>> +
>> +	for (list = 0; list < drvdata->nr_link_list; list++)
>> +		if (test_bit(list, drvdata->enable_bitmap))
>> +			return true;
>> +
>> +	return false;
>> +}
>> +
>> +static int dcc_enable(struct dcc_drvdata *drvdata, unsigned int curr_list)
>> +{
>> +	int ret;
>> +	u32 ram_cfg_base;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (!dcc_valid_list(drvdata, curr_list)) {
>> +		ret = -EINVAL;
>> +		goto out_unlock;
>> +	}
>> +
>> +	/* Fill dcc sram with the poison value.
>> +	 * This helps in understanding bus
>> +	 * hang from registers returning a zero
>> +	 */
>> +	if (!is_dcc_enabled(drvdata))
>> +		memset_io(drvdata->ram_base, 0xde, drvdata->ram_size);
>> +
>> +	/* 1. Take ownership of the list */
>> +	dcc_list_writel(drvdata, DCC_LOCK_MASK, curr_list, DCC_LL_LOCK);
>> +
>> +	/* 2. Program linked-list in the SRAM */
>> +	ram_cfg_base = drvdata->ram_cfg;
>> +	ret = dcc_emit_config(drvdata, curr_list);
>> +	if (ret) {
>> +		dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
>> +		goto out_unlock;
>> +	}
>> +
>> +	/* 3. Program DCC_RAM_CFG reg */
>> +	dcc_list_writel(drvdata, ram_cfg_base +
>> +			drvdata->ram_offset / 4, curr_list, DCC_LL_BASE);
>> +	dcc_list_writel(drvdata, drvdata->ram_start +
>> +			drvdata->ram_offset / 4, curr_list, DCC_FD_BASE);
>> +	dcc_list_writel(drvdata, 0xFFF, curr_list, DCC_LL_TIMEOUT);
>> +
>> +	/* 4. Clears interrupt status register */
>> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_INT_ENABLE);
>> +	dcc_list_writel(drvdata, (BIT(0) | BIT(1) | BIT(2)),
>> +			curr_list, DCC_LL_INT_STATUS);
>> +
>> +	set_bit(curr_list, drvdata->enable_bitmap);
>> +
>> +	/* 5. Configure trigger */
>> +	dcc_list_writel(drvdata, DCC_TRIGGER_MASK,
>> +			curr_list, DCC_LL_CFG);
>> +
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +	return ret;
>> +}
>> +
>> +static void dcc_disable(struct dcc_drvdata *drvdata, int curr_list)
>> +{
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (!test_bit(curr_list, drvdata->enable_bitmap))
>> +		goto out_unlock;
>> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_CFG);
>> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_BASE);
>> +	dcc_list_writel(drvdata, 0, curr_list, DCC_FD_BASE);
>> +	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
>> +	clear_bit(curr_list, drvdata->enable_bitmap);
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +}
>> +
>> +static u32 dcc_filp_curr_list(const struct file *filp)
>> +{
>> +	struct dentry *dentry = file_dentry(filp);
>> +	int curr_list, ret;
>> +
>> +	ret = kstrtoint(dentry->d_parent->d_name.name, 0, &curr_list);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return curr_list;
>> +}
>> +
>> +static ssize_t enable_read(struct file *filp, char __user *userbuf,
>> +			   size_t count, loff_t *ppos)
>> +{
>> +	char *buf;
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (is_dcc_enabled(drvdata))
>> +		buf = "Y\n";
>> +	else
>> +		buf = "N\n";
>> +
>> +	mutex_unlock(&drvdata->mutex);
>> +
>> +	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
>> +}
>> +
>> +static ssize_t enable_write(struct file *filp, const char __user *userbuf,
>> +			    size_t count, loff_t *ppos)
>> +{
>> +	int ret = 0, curr_list;
>> +	bool val;
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	curr_list = dcc_filp_curr_list(filp);
>> +	if (curr_list < 0)
>> +		return curr_list;
>> +
>> +	ret = kstrtobool_from_user(userbuf, count, &val);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (val) {
>> +		ret = dcc_enable(drvdata, curr_list);
>> +		if (ret)
>> +			return ret;
>> +	} else {
>> +		dcc_disable(drvdata, curr_list);
>> +	}
>> +
>> +	return count;
>> +}
>> +
>> +static const struct file_operations enable_fops = {
>> +	.read = enable_read,
>> +	.write = enable_write,
>> +	.open = simple_open,
>> +	.llseek = generic_file_llseek,
>> +};
>> +
>> +static ssize_t trigger_write(struct file *filp,
>> +			     const char __user *user_buf, size_t count,
>> +			     loff_t *ppos)
>> +{
>> +	int ret;
>> +	unsigned int val;
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	ret = kstrtouint_from_user(user_buf, count, 0, &val);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (val != 1)
>> +		return -EINVAL;
>> +
>> +	ret = dcc_sw_trigger(drvdata);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	return count;
>> +}
>> +
>> +static const struct file_operations trigger_fops = {
>> +	.write = trigger_write,
>> +	.open = simple_open,
>> +	.llseek = generic_file_llseek,
>> +};
>> +
>> +static int dcc_config_add(struct dcc_drvdata *drvdata, unsigned int addr,
>> +			  unsigned int len, bool apb_bus, int curr_list)
>> +{
>> +	int ret = 0;
>> +	struct dcc_config_entry *entry, *pentry;
>> +	unsigned int base, offset;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (!len || len > drvdata->ram_size / DCC_WORD_SIZE) {
>> +		dev_err(drvdata->dev, "DCC: Invalid length\n");
>> +		ret = -EINVAL;
>> +		goto out_unlock;
>> +	}
>> +
>> +	base = addr & DCC_ADDR_RANGE_MASK;
>> +
>> +	if (!list_empty(&drvdata->cfg_head[curr_list])) {
>> +		pentry = list_last_entry(&drvdata->cfg_head[curr_list],
>> +					 struct dcc_config_entry, list);
>> +
>> +		if (pentry->desc_type == DCC_READ_TYPE &&
>> +		    addr >= (pentry->base + pentry->offset) &&
>> +		    addr <= (pentry->base + pentry->offset + MAX_DCC_OFFSET)) {
>> +			/* Re-use base address from last entry */
>> +			base = pentry->base;
>> +
>> +			if ((pentry->len * 4 + pentry->base + pentry->offset)
>> +					== addr) {
>> +				len += pentry->len;
>> +
>> +				if (len > MAX_DCC_LEN)
>> +					pentry->len = MAX_DCC_LEN;
>> +				else
>> +					pentry->len = len;
>> +
>> +				addr = pentry->base + pentry->offset +
>> +					pentry->len * 4;
>> +				len -= pentry->len;
>> +			}
>> +		}
>> +	}
>> +
>> +	offset = addr - base;
>> +
>> +	while (len) {
>> +		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
>> +		if (!entry) {
>> +			ret = -ENOMEM;
>> +			goto out_unlock;
>> +		}
>> +
>> +		entry->base = base;
>> +		entry->offset = offset;
>> +		entry->len = min_t(u32, len, MAX_DCC_LEN);
>> +		entry->desc_type = DCC_READ_TYPE;
>> +		entry->apb_bus = apb_bus;
>> +		INIT_LIST_HEAD(&entry->list);
>> +		list_add_tail(&entry->list,
>> +			      &drvdata->cfg_head[curr_list]);
>> +
>> +		len -= entry->len;
>> +		offset += MAX_DCC_LEN * 4;
>> +	}
>> +
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +	return ret;
>> +}
>> +
>> +static ssize_t dcc_config_add_read(struct dcc_drvdata *drvdata, char *buf, int curr_list)
>> +{
>> +	bool bus;
>> +	int len, nval;
>> +	unsigned int base;
>> +	char apb_bus[4];
>> +
>> +	nval = sscanf(buf, "%x %i %3s", &base, &len, apb_bus);
>> +	if (nval <= 0 || nval > 3)
>> +		return -EINVAL;
>> +
>> +	if (nval == 1) {
>> +		len = 1;
>> +		bus = false;
>> +	} else if (nval == 2) {
>> +		bus = false;
>> +	} else if (!strcmp("apb", apb_bus)) {
>> +		bus = true;
>> +	} else if (!strcmp("ahb", apb_bus)) {
>> +		bus = false;
>> +	} else {
>> +		return -EINVAL;
>> +	}
>> +
>> +	return dcc_config_add(drvdata, base, len, bus, curr_list);
>> +}
>> +
>> +static void dcc_config_reset(struct dcc_drvdata *drvdata)
>> +{
>> +	struct dcc_config_entry *entry, *temp;
>> +	int curr_list;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
>> +		list_for_each_entry_safe(entry, temp,
>> +					 &drvdata->cfg_head[curr_list], list) {
>> +			list_del(&entry->list);
>> +			kfree(entry);
>> +		}
>> +	}
>> +	drvdata->ram_start = 0;
>> +	drvdata->ram_cfg = 0;
>> +	mutex_unlock(&drvdata->mutex);
>> +}
>> +
>> +static ssize_t config_reset_write(struct file *filp,
>> +				  const char __user *user_buf, size_t count,
>> +				  loff_t *ppos)
>> +{
>> +	unsigned int val, ret;
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	ret = kstrtouint_from_user(user_buf, count, 0, &val);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (val)
>> +		dcc_config_reset(drvdata);
>> +
>> +	return count;
>> +}
>> +
>> +static const struct file_operations config_reset_fops = {
>> +	.write = config_reset_write,
>> +	.open = simple_open,
>> +	.llseek = generic_file_llseek,
>> +};
>> +
>> +static ssize_t ready_read(struct file *filp, char __user *userbuf,
>> +			  size_t count, loff_t *ppos)
>> +{
>> +	int ret = 0;
>> +	char *buf;
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (!is_dcc_enabled(drvdata)) {
>> +		ret = -EINVAL;
>> +		goto out_unlock;
>> +	}
>> +
>> +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
>> +		buf = "Y\n";
>> +	else
>> +		buf = "N\n";
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +
>> +	if (ret < 0)
>> +		return -EINVAL;
>> +	else
> 
> You do the "lock, get a value, unlock, do something with the value"
> thing a bunch, but what prevents the value from changing after the lock
> happens?  So why is the lock needed at all?

The lock is used to prevent concurrent accesses of the drv_data when
scripts are being run from userspace.

> 
> thanks,
> 
> greg k-h
> 
>> +		return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf) + 1);
>> +}
>> +
>> +static const struct file_operations ready_fops = {
>> +	.read = ready_read,
>> +	.open = simple_open,
>> +	.llseek = generic_file_llseek,
>> +};
>> +
>> +static int dcc_add_loop(struct dcc_drvdata *drvdata, unsigned long loop_cnt, int curr_list)
>> +{
>> +	struct dcc_config_entry *entry;
>> +
>> +	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
>> +	if (!entry)
>> +		return -ENOMEM;
>> +
>> +	entry->loop_cnt = min_t(u32, loop_cnt, MAX_LOOP_CNT);
>> +	entry->desc_type = DCC_LOOP_TYPE;
>> +	INIT_LIST_HEAD(&entry->list);
>> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t dcc_config_add_loop(struct dcc_drvdata *drvdata, char *buf, int curr_list)
>> +{
>> +	int ret, i = 0;
>> +	char *token, *input;
>> +	char delim[2] = " ";
>> +	unsigned int val[MAX_LOOP_ADDR];
>> +
>> +	input = buf;
>> +
>> +	while ((token = strsep(&input, delim)) && i < MAX_LOOP_ADDR) {
>> +		ret = kstrtoint(token, 0, &val[i++]);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	if (token) {
>> +		dev_err(drvdata->dev, "Max limit %u of loop address exceeded",
>> +			MAX_LOOP_ADDR);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (val[1] < 1 || val[1] > 8)
>> +		return -EINVAL;
>> +
>> +	ret = dcc_add_loop(drvdata, val[0], curr_list);
>> +	if (ret)
>> +		return ret;
>> +
>> +	for (i = 0; i < val[1]; i++)
>> +		dcc_config_add(drvdata, val[i + 2], 1, false, curr_list);
>> +
>> +	return dcc_add_loop(drvdata, 1, curr_list);
>> +}
>> +
>> +static int dcc_rd_mod_wr_add(struct dcc_drvdata *drvdata, unsigned int mask,
>> +			     unsigned int val, int curr_list)
>> +{
>> +	int ret = 0;
>> +	struct dcc_config_entry *entry;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	if (list_empty(&drvdata->cfg_head[curr_list])) {
>> +		dev_err(drvdata->dev, "DCC: No read address programmed\n");
>> +		ret = -EPERM;
>> +		goto out_unlock;
>> +	}
>> +
>> +	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
>> +	if (!entry) {
>> +		ret = -ENOMEM;
>> +		goto out_unlock;
>> +	}
>> +
>> +	entry->desc_type = DCC_READ_WRITE_TYPE;
>> +	entry->mask = mask;
>> +	entry->write_val = val;
>> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
>> +out_unlock:
>> +	mutex_unlock(&drvdata->mutex);
>> +	return ret;
>> +}
>> +
>> +static ssize_t dcc_config_add_read_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
>> +{
>> +	int ret;
>> +	int nval;
>> +	unsigned int addr, mask, val;
>> +
>> +	nval = sscanf(buf, "%x %x %x", &addr, &mask, &val);
>> +
>> +	if (nval <= 1 || nval > 3)
>> +		return -EINVAL;
>> +
>> +	ret = dcc_config_add(drvdata, addr, 1, false, curr_list);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return dcc_rd_mod_wr_add(drvdata, mask, val, curr_list);
>> +}
>> +
>> +static int dcc_add_write(struct dcc_drvdata *drvdata, unsigned int addr,
>> +			 unsigned int write_val, int apb_bus, int curr_list)
>> +{
>> +	struct dcc_config_entry *entry;
>> +
>> +	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
>> +	if (!entry)
>> +		return -ENOMEM;
>> +
>> +	entry->desc_type = DCC_WRITE_TYPE;
>> +	entry->base = addr & GENMASK(31, 4);
>> +	entry->offset = addr - entry->base;
>> +	entry->write_val = write_val;
>> +	entry->len = 1;
>> +	entry->apb_bus = apb_bus;
>> +	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t dcc_config_add_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
>> +{
>> +	bool bus;
>> +	int nval;
>> +	unsigned int addr, write_val;
>> +	char apb_bus[4];
>> +
>> +	nval = sscanf(buf, "%x %x %3s", &addr, &write_val, apb_bus);
>> +
>> +	if (nval <= 1 || nval > 3)
>> +		return -EINVAL;
>> +
>> +	if (nval == 2)
>> +		bus = true;
>> +
>> +	if (nval == 3) {
>> +		if (!strcmp("apb", apb_bus))
>> +			bus = true;
>> +		else if (!strcmp("ahb", apb_bus))
>> +			bus = false;
>> +		else
>> +			return -EINVAL;
>> +	}
>> +
>> +	return dcc_add_write(drvdata, addr, write_val, bus, curr_list);
>> +}
>> +
>> +static int config_show(struct seq_file *m, void *data)
>> +{
>> +	struct dcc_drvdata *drvdata = m->private;
>> +	struct dcc_config_entry *entry;
>> +	int index = 0, curr_list;
>> +
>> +	curr_list = dcc_filp_curr_list(m->file);
>> +	if (curr_list < 0)
>> +		return curr_list;
>> +
>> +	mutex_lock(&drvdata->mutex);
>> +
>> +	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
>> +		index++;
>> +		switch (entry->desc_type) {
>> +		case DCC_READ_WRITE_TYPE:
>> +			seq_printf(m, "RW mask: 0x%x, val: 0x%x\n index: 0x%x\n",
>> +				   entry->mask, entry->write_val, index);
>> +			break;
>> +		case DCC_LOOP_TYPE:
>> +			seq_printf(m, "L index: 0x%x Loop: %d\n", index, entry->loop_cnt);
>> +			break;
>> +		case DCC_WRITE_TYPE:
>> +			seq_printf(m, "W Base:0x%x, Offset: 0x%x, val: 0x%x, APB: %d\n, Index: 0x%x\n",
>> +				   entry->base, entry->offset, entry->write_val, entry->apb_bus,
>> +				   index);
>> +			break;
>> +		case DCC_READ_TYPE:
>> +			seq_printf(m, "R Base:0x%x, Offset: 0x%x, len: 0x%x, APB: %d\n, Index: 0x%x\n",
>> +				   entry->base, entry->offset, entry->len, entry->apb_bus, index);
>> +		}
>> +	}
>> +	mutex_unlock(&drvdata->mutex);
>> +	return 0;
>> +}
>> +
>> +static int config_open(struct inode *inode, struct file *file)
>> +{
>> +	struct dcc_drvdata *drvdata = inode->i_private;
>> +
>> +	return single_open(file, config_show, drvdata);
>> +}
>> +
>> +static ssize_t config_write(struct file *filp,
>> +			    const char __user *user_buf, size_t count,
>> +			    loff_t *ppos)
>> +{
>> +	int ret, curr_list;
>> +	char *token, buf[50];
>> +	char *bufp = buf;
>> +	char *delim = " ";
>> +	struct dcc_drvdata *drvdata = filp->private_data;
>> +
>> +	if (count > sizeof(buf) || count == 0)
>> +		return -EINVAL;
>> +
>> +	ret = copy_from_user(buf, user_buf, count);
>> +	if (ret)
>> +		return -EFAULT;
>> +
>> +	curr_list = dcc_filp_curr_list(filp);
>> +	if (curr_list < 0)
>> +		return curr_list;
>> +
>> +	if (buf[count - 1] == '\n')
>> +		buf[count - 1] = '\0';
>> +	else
>> +		return -EINVAL;
>> +
>> +	token = strsep(&bufp, delim);
>> +
>> +	if (!strcmp("R", token)) {
>> +		ret = dcc_config_add_read(drvdata, bufp, curr_list);
>> +	} else if (!strcmp("W", token)) {
>> +		ret = dcc_config_add_write(drvdata, bufp, curr_list);
>> +	} else if (!strcmp("RW", token)) {
>> +		ret = dcc_config_add_read_write(drvdata, bufp, curr_list);
>> +	} else if (!strcmp("L", token)) {
>> +		ret = dcc_config_add_loop(drvdata, bufp, curr_list);
>> +	} else {
>> +		dev_err(drvdata->dev, "%s is not a correct input\n", token);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (ret)
>> +		return ret;
>> +
>> +	return count;
>> +}
>> +
>> +static const struct file_operations config_fops = {
>> +	.open = config_open,
>> +	.read = seq_read,
>> +	.write = config_write,
>> +	.llseek = seq_lseek,
>> +	.release = single_release,
>> +};
>> +
>> +static void dcc_delete_debug_dir(struct dcc_drvdata *drvdata)
>> +{
>> +	 debugfs_remove_recursive(drvdata->dbg_dir);
>> +};
>> +
>> +static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
>> +{
>> +	int i;
>> +	char list_num[10];
>> +	struct dentry *dcc_dev, *list;
>> +	struct device *dev = drvdata->dev;
>> +
>> +	drvdata->dbg_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
>> +	dcc_dev = debugfs_create_dir(dev_name(dev), drvdata->dbg_dir);
>> +
>> +	for (i = 0; i <= drvdata->nr_link_list; i++) {
>> +		sprintf(list_num, "%d", i);
>> +		list = debugfs_create_dir(list_num, dcc_dev);
>> +		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
>> +		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
>> +	}
>> +
>> +	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
>> +	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
>> +	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
>> +			    drvdata, &config_reset_fops);
>> +}
>> +
>> +static ssize_t dcc_sram_read(struct file *file, char __user *data,
>> +			     size_t len, loff_t *ppos)
>> +{
>> +	unsigned char *buf;
>> +	struct dcc_drvdata *drvdata;
>> +
>> +	drvdata = container_of(file->private_data, struct dcc_drvdata,
>> +			       sram_dev);
>> +
>> +	/* EOF check */
>> +	if (*ppos >= drvdata->ram_size)
>> +		return 0;
>> +
>> +	if ((*ppos + len) > drvdata->ram_size)
>> +		len = (drvdata->ram_size - *ppos);
>> +
>> +	buf = kzalloc(len, GFP_KERNEL);
>> +	if (!buf)
>> +		return -ENOMEM;
>> +
>> +	memcpy_fromio(buf, drvdata->ram_base + *ppos, len);
>> +
>> +	if (copy_to_user(data, buf, len)) {
>> +		kfree(buf);
>> +		return -EFAULT;
>> +	}
>> +
>> +	*ppos += len;
>> +
>> +	kfree(buf);
>> +
>> +	return len;
>> +}
>> +
>> +static const struct file_operations dcc_sram_fops = {
>> +	.owner		= THIS_MODULE,
>> +	.read		= dcc_sram_read,
>> +	.llseek		= no_llseek,
>> +};
>> +
>> +static int dcc_sram_dev_init(struct dcc_drvdata *drvdata)
>> +{
>> +	drvdata->sram_dev.minor = MISC_DYNAMIC_MINOR;
>> +	drvdata->sram_dev.name = "dcc_sram";
>> +	drvdata->sram_dev.fops = &dcc_sram_fops;
>> +
>> +	return misc_register(&drvdata->sram_dev);
>> +}
>> +
>> +static void dcc_sram_dev_exit(struct dcc_drvdata *drvdata)
>> +{
>> +	misc_deregister(&drvdata->sram_dev);
>> +}
>> +
>> +static int dcc_probe(struct platform_device *pdev)
>> +{
>> +	u32 val;
>> +	int ret = 0, i;
>> +	struct device *dev = &pdev->dev;
>> +	struct dcc_drvdata *drvdata;
>> +	struct resource *res;
>> +
>> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
>> +	if (!drvdata)
>> +		return -ENOMEM;
>> +
>> +	drvdata->dev = &pdev->dev;
>> +	platform_set_drvdata(pdev, drvdata);
>> +
>> +	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(drvdata->base))
>> +		return PTR_ERR(drvdata->base);
>> +
>> +	drvdata->ram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
>> +	if (IS_ERR(drvdata->ram_base))
>> +		return PTR_ERR(drvdata->ram_base);
>> +
>> +	drvdata->ram_size = resource_size(res);
>> +
>> +	drvdata->ram_offset = (size_t)of_device_get_match_data(&pdev->dev);
>> +
>> +	val = readl(drvdata->base + DCC_HW_INFO);
>> +
>> +	if (FIELD_GET(DCC_VER_INFO_MASK, val)) {
>> +		drvdata->mem_map_ver = 3;
>> +		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
>> +		if (!drvdata->nr_link_list)
>> +			return	-EINVAL;
>> +	} else if ((val & DCC_VER_MASK2) == DCC_VER_MASK2) {
>> +		drvdata->mem_map_ver = 2;
>> +		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
>> +		if (!drvdata->nr_link_list)
>> +			return	-EINVAL;
>> +	} else {
>> +		drvdata->mem_map_ver = 1;
>> +		drvdata->nr_link_list = DCC_MAX_LINK_LIST;
>> +	}
>> +
>> +	/* Either set the fixed loop offset or calculate
>> +	 * it from the total number of words in dcc_sram.
>> +	 * Max consecutive addresses dcc can loop is
>> +	 * equivalent to the words in dcc_sram.
>> +	 */
>> +	if (val & DCC_LOOP_OFFSET_MASK)
>> +		drvdata->loop_shift = DCC_FIX_LOOP_OFFSET;
>> +	else
>> +		drvdata->loop_shift = get_bitmask_order((drvdata->ram_offset +
>> +					drvdata->ram_size) / DCC_SRAM_WORD_LENGTH - 1);
>> +
>> +	mutex_init(&drvdata->mutex);
>> +
>> +	drvdata->enable_bitmap = devm_kcalloc(dev, BITS_TO_LONGS(drvdata->nr_link_list),
>> +					      sizeof(*drvdata->enable_bitmap), GFP_KERNEL);
>> +	if (!drvdata->enable_bitmap)
>> +		return -ENOMEM;
>> +
>> +	drvdata->cfg_head = devm_kcalloc(dev, drvdata->nr_link_list,
>> +					 sizeof(*drvdata->cfg_head), GFP_KERNEL);
>> +	if (!drvdata->cfg_head)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < drvdata->nr_link_list; i++)
>> +		INIT_LIST_HEAD(&drvdata->cfg_head[i]);
>> +
>> +	ret = dcc_sram_dev_init(drvdata);
>> +	if (ret) {
>> +		dev_err(drvdata->dev, "DCC: sram node not registered.\n");
>> +		return ret;
>> +	}
>> +
>> +	dcc_create_debug_dir(drvdata);
>> +
>> +	return 0;
>> +}
>> +
>> +static int dcc_remove(struct platform_device *pdev)
>> +{
>> +	struct dcc_drvdata *drvdata = platform_get_drvdata(pdev);
>> +
>> +	dcc_delete_debug_dir(drvdata);
>> +	dcc_sram_dev_exit(drvdata);
>> +	dcc_config_reset(drvdata);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id dcc_match_table[] = {
>> +	{ .compatible = "qcom,sc7180-dcc", .data = (void *)0x6000 },
>> +	{ .compatible = "qcom,sc7280-dcc", .data = (void *)0x12000 },
>> +	{ .compatible = "qcom,sdm845-dcc", .data = (void *)0x6000 },
>> +	{ .compatible = "qcom,sm8150-dcc", .data = (void *)0x5000 },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, dcc_match_table);
>> +
>> +static struct platform_driver dcc_driver = {
>> +	.probe = dcc_probe,
>> +	.remove	= dcc_remove,
>> +	.driver	= {
>> +		.name = "qcom-dcc",
>> +		.of_match_table	= dcc_match_table,
>> +	},
>> +};
>> +
>> +module_platform_driver(dcc_driver);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("Qualcomm Technologies Inc. DCC driver");
>> +
>> -- 
>> 2.17.1
>>

Greg Kroah-Hartman June 15, 2023, 12:50 p.m. UTC | #5

On Thu, Jun 15, 2023 at 06:13:53PM +0530, Souradeep Chowdhury wrote:
> 
> 
> On 6/15/2023 4:03 PM, Greg Kroah-Hartman wrote:
> > On Thu, May 04, 2023 at 11:36:22PM -0700, Souradeep Chowdhury wrote:
> > > +/**
> > > + * struct dcc_config_entry - configuration information related to each dcc instruction
> > > + * @base:                    Base address of the register to be configured in dcc
> > 
> > Why is this a u32 and not a bigger size?
> 
> Currently only 32 bit register addresses are supported for DCC
> configuration.
> 
> > 
> > > + * @offset:                  Offset to the base address to be configured in dcc
> > > + * @len:                     Length of the address in words to be configured in dcc
> > 
> > What is a "word" here, 16 bits?
> 
> Each word is 4 bytes(32 bits)

See, I guess wrong, you should say what this is :)

> > > + * @loop_cnt:                The number of times to loop on the register address in case
> > > +				of loop instructions
> > > + * @write_val:               The value to be written on the register address in case of
> > > +				write instructions
> > > + * @mask:                    Mask corresponding to the value to be written in case of
> > > +				write instructions
> > > + * @apb_bus:                 Type of bus to be used for the instruction, can be either
> > > +				'apb' or 'ahb'
> > 
> > How can a bool be either "apb" or "ahb"?
> 
> 1 stands for apb and 0 for ahb. Will update the same here.

Why not have an enum?  Will there ever be another "bus"?

> > > +static ssize_t ready_read(struct file *filp, char __user *userbuf,
> > > +			  size_t count, loff_t *ppos)
> > > +{
> > > +	int ret = 0;
> > > +	char *buf;
> > > +	struct dcc_drvdata *drvdata = filp->private_data;
> > > +
> > > +	mutex_lock(&drvdata->mutex);
> > > +
> > > +	if (!is_dcc_enabled(drvdata)) {
> > > +		ret = -EINVAL;
> > > +		goto out_unlock;
> > > +	}
> > > +
> > > +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
> > > +		buf = "Y\n";
> > > +	else
> > > +		buf = "N\n";
> > > +out_unlock:
> > > +	mutex_unlock(&drvdata->mutex);
> > > +
> > > +	if (ret < 0)
> > > +		return -EINVAL;
> > > +	else
> > 
> > You do the "lock, get a value, unlock, do something with the value"
> > thing a bunch, but what prevents the value from changing after the lock
> > happens?  So why is the lock needed at all?
> 
> The lock is used to prevent concurrent accesses of the drv_data when
> scripts are being run from userspace.

How would that matter?  The state can change instantly after the lock is
given up, and then the returned value is now incorrect.  So no need for
a lock at all as you really aren't "protecting" anything, or am I
missing something else?

thanks,

greg k-h

Souradeep Chowdhury June 15, 2023, 1:47 p.m. UTC | #6

On 6/15/2023 6:20 PM, Greg Kroah-Hartman wrote:
> On Thu, Jun 15, 2023 at 06:13:53PM +0530, Souradeep Chowdhury wrote:
>>
>>
>> On 6/15/2023 4:03 PM, Greg Kroah-Hartman wrote:
>>> On Thu, May 04, 2023 at 11:36:22PM -0700, Souradeep Chowdhury wrote:
>>>> +/**
>>>> + * struct dcc_config_entry - configuration information related to each dcc instruction
>>>> + * @base:                    Base address of the register to be configured in dcc
>>>
>>> Why is this a u32 and not a bigger size?
>>
>> Currently only 32 bit register addresses are supported for DCC
>> configuration.
>>
>>>
>>>> + * @offset:                  Offset to the base address to be configured in dcc
>>>> + * @len:                     Length of the address in words to be configured in dcc
>>>
>>> What is a "word" here, 16 bits?
>>
>> Each word is 4 bytes(32 bits)
> 
> See, I guess wrong, you should say what this is :)

Ack

> 
>>>> + * @loop_cnt:                The number of times to loop on the register address in case
>>>> +				of loop instructions
>>>> + * @write_val:               The value to be written on the register address in case of
>>>> +				write instructions
>>>> + * @mask:                    Mask corresponding to the value to be written in case of
>>>> +				write instructions
>>>> + * @apb_bus:                 Type of bus to be used for the instruction, can be either
>>>> +				'apb' or 'ahb'
>>>
>>> How can a bool be either "apb" or "ahb"?
>>
>> 1 stands for apb and 0 for ahb. Will update the same here.
> 
> Why not have an enum?  Will there ever be another "bus"?

No, only these two are supported for dcc.

> 
>>>> +static ssize_t ready_read(struct file *filp, char __user *userbuf,
>>>> +			  size_t count, loff_t *ppos)
>>>> +{
>>>> +	int ret = 0;
>>>> +	char *buf;
>>>> +	struct dcc_drvdata *drvdata = filp->private_data;
>>>> +
>>>> +	mutex_lock(&drvdata->mutex);
>>>> +
>>>> +	if (!is_dcc_enabled(drvdata)) {
>>>> +		ret = -EINVAL;
>>>> +		goto out_unlock;
>>>> +	}
>>>> +
>>>> +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
>>>> +		buf = "Y\n";
>>>> +	else
>>>> +		buf = "N\n";
>>>> +out_unlock:
>>>> +	mutex_unlock(&drvdata->mutex);
>>>> +
>>>> +	if (ret < 0)
>>>> +		return -EINVAL;
>>>> +	else
>>>
>>> You do the "lock, get a value, unlock, do something with the value"
>>> thing a bunch, but what prevents the value from changing after the lock
>>> happens?  So why is the lock needed at all?
>>
>> The lock is used to prevent concurrent accesses of the drv_data when
>> scripts are being run from userspace.
> 
> How would that matter?  The state can change instantly after the lock is
> given up, and then the returned value is now incorrect.  So no need for
> a lock at all as you really aren't "protecting" anything, or am I
> missing something else?

This lock is needed to protect the access to the global instance of 
drv_data structure instantiated at probe time within each individual 
callbacks of debugfs.

> 
> thanks,
> 
> greg k-h

Greg Kroah-Hartman June 15, 2023, 2:06 p.m. UTC | #7

On Thu, Jun 15, 2023 at 07:17:34PM +0530, Souradeep Chowdhury wrote:
> > > > > +static ssize_t ready_read(struct file *filp, char __user *userbuf,
> > > > > +			  size_t count, loff_t *ppos)
> > > > > +{
> > > > > +	int ret = 0;
> > > > > +	char *buf;
> > > > > +	struct dcc_drvdata *drvdata = filp->private_data;
> > > > > +
> > > > > +	mutex_lock(&drvdata->mutex);
> > > > > +
> > > > > +	if (!is_dcc_enabled(drvdata)) {
> > > > > +		ret = -EINVAL;
> > > > > +		goto out_unlock;
> > > > > +	}
> > > > > +
> > > > > +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
> > > > > +		buf = "Y\n";
> > > > > +	else
> > > > > +		buf = "N\n";
> > > > > +out_unlock:
> > > > > +	mutex_unlock(&drvdata->mutex);
> > > > > +
> > > > > +	if (ret < 0)
> > > > > +		return -EINVAL;
> > > > > +	else
> > > > 
> > > > You do the "lock, get a value, unlock, do something with the value"
> > > > thing a bunch, but what prevents the value from changing after the lock
> > > > happens?  So why is the lock needed at all?
> > > 
> > > The lock is used to prevent concurrent accesses of the drv_data when
> > > scripts are being run from userspace.
> > 
> > How would that matter?  The state can change instantly after the lock is
> > given up, and then the returned value is now incorrect.  So no need for
> > a lock at all as you really aren't "protecting" anything, or am I
> > missing something else?
> 
> This lock is needed to protect the access to the global instance of drv_data
> structure instantiated at probe time within each individual callbacks of
> debugfs.

What exactly are you "protecting" here that could change in a way that
cause a problem?

You aren't returning a value that is ever guaranteed to be "correct"
except that it happened sometime in the past, it might be right anymore.

thanks,

greg k-h

Souradeep Chowdhury June 21, 2023, 9:18 a.m. UTC | #8

On 6/15/2023 7:36 PM, Greg Kroah-Hartman wrote:
> On Thu, Jun 15, 2023 at 07:17:34PM +0530, Souradeep Chowdhury wrote:
>>>>>> +static ssize_t ready_read(struct file *filp, char __user *userbuf,
>>>>>> +			  size_t count, loff_t *ppos)
>>>>>> +{
>>>>>> +	int ret = 0;
>>>>>> +	char *buf;
>>>>>> +	struct dcc_drvdata *drvdata = filp->private_data;
>>>>>> +
>>>>>> +	mutex_lock(&drvdata->mutex);
>>>>>> +
>>>>>> +	if (!is_dcc_enabled(drvdata)) {
>>>>>> +		ret = -EINVAL;
>>>>>> +		goto out_unlock;
>>>>>> +	}
>>>>>> +
>>>>>> +	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
>>>>>> +		buf = "Y\n";
>>>>>> +	else
>>>>>> +		buf = "N\n";
>>>>>> +out_unlock:
>>>>>> +	mutex_unlock(&drvdata->mutex);
>>>>>> +
>>>>>> +	if (ret < 0)
>>>>>> +		return -EINVAL;
>>>>>> +	else
>>>>>
>>>>> You do the "lock, get a value, unlock, do something with the value"
>>>>> thing a bunch, but what prevents the value from changing after the lock
>>>>> happens?  So why is the lock needed at all?
>>>>
>>>> The lock is used to prevent concurrent accesses of the drv_data when
>>>> scripts are being run from userspace.
>>>
>>> How would that matter?  The state can change instantly after the lock is
>>> given up, and then the returned value is now incorrect.  So no need for
>>> a lock at all as you really aren't "protecting" anything, or am I
>>> missing something else?
>>
>> This lock is needed to protect the access to the global instance of drv_data
>> structure instantiated at probe time within each individual callbacks of
>> debugfs.
> 
> What exactly are you "protecting" here that could change in a way that
> cause a problem?
> 
> You aren't returning a value that is ever guaranteed to be "correct"
> except that it happened sometime in the past, it might be right anymore.

Hi Greg,

The lock doesn't add any value in this particular case and I will be 
dropping it from here but in other cases it is being used to protect the 
concurrent access of the data-structures used inside the drv_data mainly 
the list which is being used to append register configurations, write 
the configuration to the dcc_sram and also delete it while doing a 
config reset. The lock is also used in case of software trigger to read 
the bitmap of the lists to set register values.

Thanks,
Souradeep

> 
> thanks,
> 
> greg k-h

Patch

diff --git a/Documentation/ABI/testing/debugfs-driver-dcc b/Documentation/ABI/testing/debugfs-driver-dcc
index 27ed5919d21b..7f588580a906 100644
--- a/Documentation/ABI/testing/debugfs-driver-dcc
+++ b/Documentation/ABI/testing/debugfs-driver-dcc
@@ -1,4 +1,4 @@ 
-What:           /sys/kernel/debug/dcc/.../ready
+What:           /sys/kernel/debug/qcom-dcc/.../ready
 Date:           December 2022
 Contact:        Souradeep Chowdhury <[e-mail]>
 Description:
@@ -6,7 +6,7 @@  Description:
 		hardware if it's ready to receive user configurations.
 		A 'Y' here indicates dcc is ready.
 
-What:           /sys/kernel/debug/dcc/.../trigger
+What:           /sys/kernel/debug/qcom-dcc/.../trigger
 Date:           December 2022
 Contact:        Souradeep Chowdhury <[e-mail]>
 Description:
@@ -14,7 +14,7 @@  Description:
 		triggers. The trigger can be invoked by writing '1'
 		to the file.
 
-What:           /sys/kernel/debug/dcc/.../config_reset
+What:           /sys/kernel/debug/qcom-dcc/.../config_reset
 Date:           December 2022
 Contact:        Souradeep Chowdhury <[e-mail]>
 Description:
@@ -24,7 +24,7 @@  Description:
 		stored in the driver gets removed and users need to
 		reconfigure addresses again.
 
-What:           /sys/kernel/debug/dcc/.../[list-number]/config
+What:           /sys/kernel/debug/qcom-dcc/.../[list-number]/config
 Date:		 December 2022
 Contact:        Souradeep Chowdhury <[e-mail]>
 Description:
@@ -109,7 +109,7 @@  Description:
 		    <address>
 			Space-separated list of addresses.
 
-What:           /sys/kernel/debug/dcc/.../[list-number]/enable
+What:           /sys/kernel/debug/qcom-dcc/.../[list-number]/enable
 Date:           December 2022
 Contact:        Souradeep Chowdhury <[e-mail]>
 Description:
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 433aa4197785..3112dbb15cf4 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -276,6 +276,15 @@  config QCOM_COINCELL
 	  to maintain PMIC register and RTC state in the absence of
 	  external power.
 
+config QCOM_DCC
+	tristate "Qualcomm Technologies, Inc. Data Capture and Compare(DCC) engine driver"
+	depends on ARCH_QCOM || COMPILE_TEST
+	help
+	  This option enables driver for Data Capture and Compare engine. DCC
+	  driver provides interface to configure DCC block and read back
+	  captured data from DCC's internal SRAM. The module name for this
+	  is qcom-dcc.ko
+
 config QCOM_FASTRPC
 	tristate "Qualcomm FastRPC"
 	depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 56de43943cd5..dced656e2b37 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -16,6 +16,7 @@  obj-$(CONFIG_TIFM_CORE)       	+= tifm_core.o
 obj-$(CONFIG_TIFM_7XX1)       	+= tifm_7xx1.o
 obj-$(CONFIG_PHANTOM)		+= phantom.o
 obj-$(CONFIG_QCOM_COINCELL)	+= qcom-coincell.o
+obj-$(CONFIG_QCOM_DCC)		+= qcom-dcc.o
 obj-$(CONFIG_QCOM_FASTRPC)	+= fastrpc.o
 obj-$(CONFIG_SENSORS_BH1770)	+= bh1770glc.o
 obj-$(CONFIG_SENSORS_APDS990X)	+= apds990x.o
diff --git a/drivers/misc/qcom-dcc.c b/drivers/misc/qcom-dcc.c
new file mode 100644
index 000000000000..34f0c4d9999d
--- /dev/null
+++ b/drivers/misc/qcom-dcc.c
@@ -0,0 +1,1325 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2022-2023, Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#define STATUS_READY_TIMEOUT		5000  /* microseconds */
+
+/* DCC registers */
+#define DCC_HW_INFO			0x04
+#define DCC_LL_NUM_INFO			0x10
+#define DCC_LL_LOCK			0x00
+#define DCC_LL_CFG			0x04
+#define DCC_LL_BASE			0x08
+#define DCC_FD_BASE			0x0c
+#define DCC_LL_OFFSET                   0x80
+#define DCC_LL_TIMEOUT			0x10
+#define DCC_LL_INT_ENABLE		0x18
+#define DCC_LL_INT_STATUS		0x1c
+#define DCC_LL_SW_TRIGGER		0x2c
+#define DCC_LL_BUS_ACCESS_STATUS	0x30
+
+/* Default value used if a bit 6 in the HW_INFO register is set. */
+#define DCC_FIX_LOOP_OFFSET		16
+
+/* Mask to find version info from HW_Info register */
+#define DCC_VER_INFO_MASK		BIT(9)
+
+#define MAX_DCC_OFFSET			GENMASK(9, 2)
+#define MAX_DCC_LEN			GENMASK(6, 0)
+#define MAX_LOOP_CNT			GENMASK(7, 0)
+#define MAX_LOOP_ADDR			10
+
+#define DCC_ADDR_DESCRIPTOR		0x00
+#define DCC_ADDR_LIMIT			27
+#define DCC_WORD_SIZE			sizeof(u32)
+#define DCC_ADDR_RANGE_MASK		GENMASK(31, 4)
+#define DCC_LOOP_DESCRIPTOR		BIT(30)
+#define DCC_RD_MOD_WR_DESCRIPTOR	BIT(31)
+#define DCC_LINK_DESCRIPTOR		GENMASK(31, 30)
+#define DCC_STATUS_MASK			GENMASK(1, 0)
+#define DCC_LOCK_MASK			BIT(0)
+#define DCC_LOOP_OFFSET_MASK		BIT(6)
+#define DCC_TRIGGER_MASK		BIT(9)
+
+#define DCC_WRITE_MASK			BIT(15)
+#define DCC_WRITE_OFF_MASK		GENMASK(7, 0)
+#define DCC_WRITE_LEN_MASK		GENMASK(14, 8)
+
+#define DCC_READ_IND			0x00
+#define DCC_WRITE_IND			(BIT(28))
+
+#define DCC_AHB_IND			0x00
+#define DCC_APB_IND			BIT(29)
+
+#define DCC_MAX_LINK_LIST		8
+
+#define DCC_VER_MASK2			GENMASK(5, 0)
+
+#define DCC_SRAM_WORD_LENGTH		4
+
+#define DCC_RD_MOD_WR_ADDR              0xC105E
+
+enum dcc_descriptor_type {
+	DCC_READ_TYPE,
+	DCC_LOOP_TYPE,
+	DCC_READ_WRITE_TYPE,
+	DCC_WRITE_TYPE
+};
+
+/**
+ * struct dcc_config_entry - configuration information related to each dcc instruction
+ * @base:                    Base address of the register to be configured in dcc
+ * @offset:                  Offset to the base address to be configured in dcc
+ * @len:                     Length of the address in words to be configured in dcc
+ * @loop_cnt:                The number of times to loop on the register address in case
+				of loop instructions
+ * @write_val:               The value to be written on the register address in case of
+				write instructions
+ * @mask:                    Mask corresponding to the value to be written in case of
+				write instructions
+ * @apb_bus:                 Type of bus to be used for the instruction, can be either
+				'apb' or 'ahb'
+ * @desc_type:               Stores the type of dcc instruction
+ * @list:                    This is used to append this instruction to the list of
+				instructions
+ */
+struct dcc_config_entry {
+	u32				base;
+	u32				offset;
+	u32				len;
+	u32				loop_cnt;
+	u32				write_val;
+	u32				mask;
+	bool				apb_bus;
+	enum dcc_descriptor_type	desc_type;
+	struct list_head		list;
+};
+
+/**
+ * struct dcc_drvdata - configuration information related to a dcc device
+ * @base:		Base Address of the dcc device
+ * @dev:		The device attached to the driver data
+ * @mutex:		Lock to protect access and manipulation of dcc_drvdata
+ * @ram_base:		Base address for the SRAM dedicated for the dcc device
+ * @ram_size:		Total size of the SRAM dedicated for the dcc device
+ * @ram_offset:		Offset to the SRAM dedicated for dcc device
+ * @mem_map_ver:	Memory map version of DCC hardware
+ * @ram_cfg:		Used for address limit calculation for dcc
+ * @ram_start:		Starting address of DCC SRAM
+ * @sram_dev:		Miscellaneous device equivalent of dcc SRAM
+ * @cfg_head:		Points to the head of the linked list of addresses
+ * @dbg_dir:		The dcc debugfs directory under which all the debugfs files are placed
+ * @nr_link_list:	Total number of linkedlists supported by the DCC configuration
+ * @loop_shift:		Loop offset bits range for the addresses
+ * @enable_bitmap:	Bitmap to capture the enabled status of each linked list of addresses
+ */
+struct dcc_drvdata {
+	void __iomem		*base;
+	void __iomem            *ram_base;
+	struct device		*dev;
+	struct mutex		mutex;
+	size_t			ram_size;
+	size_t			ram_offset;
+	int			mem_map_ver;
+	unsigned int		ram_cfg;
+	unsigned int		ram_start;
+	struct miscdevice	sram_dev;
+	struct list_head	*cfg_head;
+	struct dentry		*dbg_dir;
+	size_t			nr_link_list;
+	u8			loop_shift;
+	unsigned long		*enable_bitmap;
+};
+
+struct dcc_cfg_attr {
+	u32	addr;
+	u32	prev_addr;
+	u32	prev_off;
+	u32	link;
+	u32	sram_offset;
+};
+
+struct dcc_cfg_loop_attr {
+	u32	loop_cnt;
+	u32	loop_len;
+	u32	loop_off;
+	bool    loop_start;
+};
+
+static inline u32 dcc_status(int version)
+{
+	return version == 1 ? 0x0c : 0x1c;
+}
+
+static inline u32 dcc_list_offset(int version)
+{
+	if (version == 1)
+		return 0x1c;
+	else if (version == 2)
+		return 0x2c;
+	else
+		return 0x34;
+}
+
+static inline void dcc_list_writel(struct dcc_drvdata *drvdata,
+				   u32 ll, u32 val, u32 off)
+{
+	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
+
+	writel(val, drvdata->base + ll * DCC_LL_OFFSET + offset);
+}
+
+static inline u32 dcc_list_readl(struct dcc_drvdata *drvdata, u32 ll, u32 off)
+{
+	u32 offset = dcc_list_offset(drvdata->mem_map_ver) + off;
+
+	return readl(drvdata->base + ll * DCC_LL_OFFSET + offset);
+}
+
+static void dcc_sram_write_auto(struct dcc_drvdata *drvdata,
+				u32 val, u32 *off)
+{
+	/* If the overflow condition is met increment the offset
+	 * and return to indicate that overflow has occurred
+	 */
+	if (unlikely(*off > drvdata->ram_size - 4)) {
+		*off += 4;
+		return;
+	}
+
+	writel(val, drvdata->ram_base + *off);
+
+	*off += 4;
+}
+
+static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
+{
+	void __iomem *addr;
+	int i;
+	u32 status;
+	u32 ll_cfg;
+	u32 tmp_ll_cfg;
+	u32 val;
+	int ret = 0;
+
+	mutex_lock(&drvdata->mutex);
+
+	for (i = 0; i < drvdata->nr_link_list; i++) {
+		if (!test_bit(i, drvdata->enable_bitmap))
+			continue;
+		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
+		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
+		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
+		dcc_list_writel(drvdata, 1, i, DCC_LL_SW_TRIGGER);
+		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
+	}
+
+	addr = drvdata->base + dcc_status(drvdata->mem_map_ver);
+	if (readl_poll_timeout(addr, val, !FIELD_GET(DCC_STATUS_MASK, val),
+			       1, STATUS_READY_TIMEOUT)) {
+		dev_err(drvdata->dev, "DCC is busy after receiving sw trigger\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	for (i = 0; i < drvdata->nr_link_list; i++) {
+		if (!test_bit(i, drvdata->enable_bitmap))
+			continue;
+
+		status = dcc_list_readl(drvdata, i, DCC_LL_BUS_ACCESS_STATUS);
+		if (!status)
+			continue;
+
+		dev_err(drvdata->dev, "Read access error for list %d err: 0x%x\n",
+			i, status);
+		ll_cfg = dcc_list_readl(drvdata, i, DCC_LL_CFG);
+		tmp_ll_cfg = ll_cfg & ~DCC_TRIGGER_MASK;
+		dcc_list_writel(drvdata, tmp_ll_cfg, i, DCC_LL_CFG);
+		dcc_list_writel(drvdata, DCC_STATUS_MASK, i, DCC_LL_BUS_ACCESS_STATUS);
+		dcc_list_writel(drvdata, ll_cfg, i, DCC_LL_CFG);
+		ret = -ENODATA;
+		break;
+	}
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static void dcc_ll_cfg_reset_link(struct dcc_cfg_attr *cfg)
+{
+	cfg->addr = 0x00;
+	cfg->link = 0;
+	cfg->prev_off = 0;
+	cfg->prev_addr = cfg->addr;
+}
+
+static void dcc_emit_read_write(struct dcc_drvdata *drvdata,
+				struct dcc_config_entry *entry,
+				struct dcc_cfg_attr *cfg)
+{
+	if (cfg->link) {
+		/*
+		 * write new offset = 1 to continue
+		 * processing the list
+		 */
+
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		dcc_ll_cfg_reset_link(cfg);
+	}
+
+	cfg->addr = DCC_RD_MOD_WR_DESCRIPTOR;
+	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->mask, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
+
+	cfg->addr = 0;
+}
+
+static void dcc_emit_loop(struct dcc_drvdata *drvdata, struct dcc_config_entry *entry,
+			  struct dcc_cfg_attr *cfg,
+			  struct dcc_cfg_loop_attr *cfg_loop,
+			  u32 *total_len)
+{
+	int loop;
+
+	/* Check if we need to write link of prev entry */
+	if (cfg->link)
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+	if (cfg_loop->loop_start) {
+		loop = (cfg->sram_offset - cfg_loop->loop_off) / 4;
+		loop |= (cfg_loop->loop_cnt << drvdata->loop_shift) &
+				   GENMASK(DCC_ADDR_LIMIT, drvdata->loop_shift);
+		loop |= DCC_LOOP_DESCRIPTOR;
+		*total_len += (*total_len - cfg_loop->loop_len) * cfg_loop->loop_cnt;
+
+		dcc_sram_write_auto(drvdata, loop, &cfg->sram_offset);
+
+		cfg_loop->loop_start = false;
+		cfg_loop->loop_len = 0;
+		cfg_loop->loop_off = 0;
+	} else {
+		cfg_loop->loop_start = true;
+		cfg_loop->loop_cnt = entry->loop_cnt - 1;
+		cfg_loop->loop_len = *total_len;
+		cfg_loop->loop_off = cfg->sram_offset;
+	}
+
+	/* Reset link and prev_off */
+	dcc_ll_cfg_reset_link(cfg);
+}
+
+static void dcc_emit_write(struct dcc_drvdata *drvdata,
+			   struct dcc_config_entry *entry,
+			   struct dcc_cfg_attr *cfg)
+{
+	u32 off;
+
+	if (cfg->link) {
+		/*
+		 * write new offset = 1 to continue
+		 * processing the list
+		 */
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		cfg->addr = 0x00;
+		cfg->prev_off = 0;
+		cfg->prev_addr = cfg->addr;
+	}
+
+	off = entry->offset / 4;
+	/* write new offset-length pair to correct position */
+	cfg->link |= ((off & DCC_WRITE_OFF_MASK) | DCC_WRITE_MASK |
+		      FIELD_PREP(DCC_WRITE_LEN_MASK, entry->len));
+	cfg->link |= DCC_LINK_DESCRIPTOR;
+
+	/* Address type */
+	cfg->addr = (entry->base >> 4) & GENMASK(DCC_ADDR_LIMIT, 0);
+	if (entry->apb_bus)
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_APB_IND;
+	else
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_AHB_IND;
+	dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+
+	dcc_sram_write_auto(drvdata, entry->write_val, &cfg->sram_offset);
+
+	cfg->addr = 0x00;
+	cfg->link = 0;
+}
+
+static int dcc_emit_read(struct dcc_drvdata *drvdata,
+			 struct dcc_config_entry *entry,
+			 struct dcc_cfg_attr *cfg,
+			 u32 *pos, u32 *total_len)
+{
+	u32 off;
+	u32 temp_off;
+
+	cfg->addr = (entry->base >> 4) & GENMASK(27, 0);
+
+	if (entry->apb_bus)
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_APB_IND;
+	else
+		cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_AHB_IND;
+
+	off = entry->offset / 4;
+
+	*total_len += entry->len * 4;
+
+	if (!cfg->prev_addr || cfg->prev_addr != cfg->addr || cfg->prev_off > off) {
+		/* Check if we need to write prev link entry */
+		if (cfg->link)
+			dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+		dev_dbg(drvdata->dev, "DCC: sram address 0x%x\n", cfg->sram_offset);
+
+		/* Write address */
+		dcc_sram_write_auto(drvdata, cfg->addr, &cfg->sram_offset);
+
+		/* Reset link and prev_off */
+		cfg->link = 0;
+		cfg->prev_off = 0;
+	}
+
+	if ((off - cfg->prev_off) > 0xff || entry->len > MAX_DCC_LEN) {
+		dev_err(drvdata->dev, "DCC: Programming error Base: 0x%x, offset 0x%x\n",
+			entry->base, entry->offset);
+		return -EINVAL;
+	}
+
+	if (cfg->link) {
+		/*
+		 * link already has one offset-length so new
+		 * offset-length needs to be placed at
+		 * bits [29:15]
+		 */
+		*pos = 15;
+
+		/* Clear bits [31:16] */
+		cfg->link &= GENMASK(14, 0);
+	} else {
+		/*
+		 * link is empty, so new offset-length needs
+		 * to be placed at bits [15:0]
+		 */
+		*pos = 0;
+		cfg->link = 1 << 15;
+	}
+
+	/* write new offset-length pair to correct position */
+	temp_off = (off - cfg->prev_off) & GENMASK(7, 0);
+	cfg->link |= temp_off | ((entry->len << 8) & GENMASK(14, 8)) << *pos;
+
+	cfg->link |= DCC_LINK_DESCRIPTOR;
+
+	if (*pos) {
+		dcc_sram_write_auto(drvdata, cfg->link, &cfg->sram_offset);
+		cfg->link = 0;
+	}
+
+	cfg->prev_off  = off + entry->len - 1;
+	cfg->prev_addr = cfg->addr;
+	return 0;
+}
+
+static int dcc_emit_config(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	int ret;
+	u32 total_len, pos;
+	struct dcc_config_entry *entry;
+	struct dcc_cfg_attr cfg = {0};
+	struct dcc_cfg_loop_attr cfg_loop = {0};
+
+	cfg.sram_offset = drvdata->ram_cfg * 4;
+	total_len = 0;
+
+	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
+		switch (entry->desc_type) {
+		case DCC_READ_WRITE_TYPE:
+			dcc_emit_read_write(drvdata, entry, &cfg);
+			break;
+
+		case DCC_LOOP_TYPE:
+			dcc_emit_loop(drvdata, entry, &cfg, &cfg_loop, &total_len);
+			break;
+
+		case DCC_WRITE_TYPE:
+			dcc_emit_write(drvdata, entry, &cfg);
+			break;
+
+		case DCC_READ_TYPE:
+			ret = dcc_emit_read(drvdata, entry, &cfg, &pos, &total_len);
+			if (ret)
+				goto err;
+			break;
+		}
+	}
+
+	if (cfg.link)
+		dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
+
+	if (cfg_loop.loop_start) {
+		dev_err(drvdata->dev, "DCC: Programming error: Loop unterminated\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* Handling special case of list ending with a rd_mod_wr */
+	if (cfg.addr == DCC_RD_MOD_WR_DESCRIPTOR) {
+		cfg.addr = (DCC_RD_MOD_WR_ADDR) & GENMASK(27, 0);
+		cfg.addr |= DCC_ADDR_DESCRIPTOR;
+		dcc_sram_write_auto(drvdata, cfg.addr, &cfg.sram_offset);
+	}
+
+	/* Setting zero to indicate end of the list */
+	cfg.link = DCC_LINK_DESCRIPTOR;
+	dcc_sram_write_auto(drvdata, cfg.link, &cfg.sram_offset);
+
+	/* Check if sram offset exceeds the ram size */
+	if (cfg.sram_offset > drvdata->ram_size)
+		goto overstep;
+
+	/* Update ram_cfg and check if the data will overstep */
+	drvdata->ram_cfg = (cfg.sram_offset + total_len) / 4;
+
+	if (cfg.sram_offset + total_len > drvdata->ram_size) {
+		cfg.sram_offset += total_len;
+		goto overstep;
+	}
+
+	drvdata->ram_start = cfg.sram_offset / 4;
+	return 0;
+overstep:
+	ret = -EINVAL;
+	memset_io(drvdata->ram_base, 0, drvdata->ram_size);
+
+err:
+	return ret;
+}
+
+static bool dcc_valid_list(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	u32 lock_reg;
+
+	if (list_empty(&drvdata->cfg_head[curr_list]))
+		return false;
+
+	if (test_bit(curr_list, drvdata->enable_bitmap)) {
+		dev_err(drvdata->dev, "List %d is already enabled\n", curr_list);
+		return false;
+	}
+
+	lock_reg = dcc_list_readl(drvdata, curr_list, DCC_LL_LOCK);
+	if (lock_reg & DCC_LOCK_MASK) {
+		dev_err(drvdata->dev, "List %d is already locked\n", curr_list);
+		return false;
+	}
+
+	return true;
+}
+
+static bool is_dcc_enabled(struct dcc_drvdata *drvdata)
+{
+	int list;
+
+	for (list = 0; list < drvdata->nr_link_list; list++)
+		if (test_bit(list, drvdata->enable_bitmap))
+			return true;
+
+	return false;
+}
+
+static int dcc_enable(struct dcc_drvdata *drvdata, unsigned int curr_list)
+{
+	int ret;
+	u32 ram_cfg_base;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!dcc_valid_list(drvdata, curr_list)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/* Fill dcc sram with the poison value.
+	 * This helps in understanding bus
+	 * hang from registers returning a zero
+	 */
+	if (!is_dcc_enabled(drvdata))
+		memset_io(drvdata->ram_base, 0xde, drvdata->ram_size);
+
+	/* 1. Take ownership of the list */
+	dcc_list_writel(drvdata, DCC_LOCK_MASK, curr_list, DCC_LL_LOCK);
+
+	/* 2. Program linked-list in the SRAM */
+	ram_cfg_base = drvdata->ram_cfg;
+	ret = dcc_emit_config(drvdata, curr_list);
+	if (ret) {
+		dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
+		goto out_unlock;
+	}
+
+	/* 3. Program DCC_RAM_CFG reg */
+	dcc_list_writel(drvdata, ram_cfg_base +
+			drvdata->ram_offset / 4, curr_list, DCC_LL_BASE);
+	dcc_list_writel(drvdata, drvdata->ram_start +
+			drvdata->ram_offset / 4, curr_list, DCC_FD_BASE);
+	dcc_list_writel(drvdata, 0xFFF, curr_list, DCC_LL_TIMEOUT);
+
+	/* 4. Clears interrupt status register */
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_INT_ENABLE);
+	dcc_list_writel(drvdata, (BIT(0) | BIT(1) | BIT(2)),
+			curr_list, DCC_LL_INT_STATUS);
+
+	set_bit(curr_list, drvdata->enable_bitmap);
+
+	/* 5. Configure trigger */
+	dcc_list_writel(drvdata, DCC_TRIGGER_MASK,
+			curr_list, DCC_LL_CFG);
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static void dcc_disable(struct dcc_drvdata *drvdata, int curr_list)
+{
+	mutex_lock(&drvdata->mutex);
+
+	if (!test_bit(curr_list, drvdata->enable_bitmap))
+		goto out_unlock;
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_CFG);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_BASE);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_FD_BASE);
+	dcc_list_writel(drvdata, 0, curr_list, DCC_LL_LOCK);
+	clear_bit(curr_list, drvdata->enable_bitmap);
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+}
+
+static u32 dcc_filp_curr_list(const struct file *filp)
+{
+	struct dentry *dentry = file_dentry(filp);
+	int curr_list, ret;
+
+	ret = kstrtoint(dentry->d_parent->d_name.name, 0, &curr_list);
+	if (ret)
+		return ret;
+
+	return curr_list;
+}
+
+static ssize_t enable_read(struct file *filp, char __user *userbuf,
+			   size_t count, loff_t *ppos)
+{
+	char *buf;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (is_dcc_enabled(drvdata))
+		buf = "Y\n";
+	else
+		buf = "N\n";
+
+	mutex_unlock(&drvdata->mutex);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
+}
+
+static ssize_t enable_write(struct file *filp, const char __user *userbuf,
+			    size_t count, loff_t *ppos)
+{
+	int ret = 0, curr_list;
+	bool val;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	curr_list = dcc_filp_curr_list(filp);
+	if (curr_list < 0)
+		return curr_list;
+
+	ret = kstrtobool_from_user(userbuf, count, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val) {
+		ret = dcc_enable(drvdata, curr_list);
+		if (ret)
+			return ret;
+	} else {
+		dcc_disable(drvdata, curr_list);
+	}
+
+	return count;
+}
+
+static const struct file_operations enable_fops = {
+	.read = enable_read,
+	.write = enable_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static ssize_t trigger_write(struct file *filp,
+			     const char __user *user_buf, size_t count,
+			     loff_t *ppos)
+{
+	int ret;
+	unsigned int val;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	ret = kstrtouint_from_user(user_buf, count, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	ret = dcc_sw_trigger(drvdata);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static const struct file_operations trigger_fops = {
+	.write = trigger_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static int dcc_config_add(struct dcc_drvdata *drvdata, unsigned int addr,
+			  unsigned int len, bool apb_bus, int curr_list)
+{
+	int ret = 0;
+	struct dcc_config_entry *entry, *pentry;
+	unsigned int base, offset;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!len || len > drvdata->ram_size / DCC_WORD_SIZE) {
+		dev_err(drvdata->dev, "DCC: Invalid length\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	base = addr & DCC_ADDR_RANGE_MASK;
+
+	if (!list_empty(&drvdata->cfg_head[curr_list])) {
+		pentry = list_last_entry(&drvdata->cfg_head[curr_list],
+					 struct dcc_config_entry, list);
+
+		if (pentry->desc_type == DCC_READ_TYPE &&
+		    addr >= (pentry->base + pentry->offset) &&
+		    addr <= (pentry->base + pentry->offset + MAX_DCC_OFFSET)) {
+			/* Re-use base address from last entry */
+			base = pentry->base;
+
+			if ((pentry->len * 4 + pentry->base + pentry->offset)
+					== addr) {
+				len += pentry->len;
+
+				if (len > MAX_DCC_LEN)
+					pentry->len = MAX_DCC_LEN;
+				else
+					pentry->len = len;
+
+				addr = pentry->base + pentry->offset +
+					pentry->len * 4;
+				len -= pentry->len;
+			}
+		}
+	}
+
+	offset = addr - base;
+
+	while (len) {
+		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+		if (!entry) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+
+		entry->base = base;
+		entry->offset = offset;
+		entry->len = min_t(u32, len, MAX_DCC_LEN);
+		entry->desc_type = DCC_READ_TYPE;
+		entry->apb_bus = apb_bus;
+		INIT_LIST_HEAD(&entry->list);
+		list_add_tail(&entry->list,
+			      &drvdata->cfg_head[curr_list]);
+
+		len -= entry->len;
+		offset += MAX_DCC_LEN * 4;
+	}
+
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static ssize_t dcc_config_add_read(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	bool bus;
+	int len, nval;
+	unsigned int base;
+	char apb_bus[4];
+
+	nval = sscanf(buf, "%x %i %3s", &base, &len, apb_bus);
+	if (nval <= 0 || nval > 3)
+		return -EINVAL;
+
+	if (nval == 1) {
+		len = 1;
+		bus = false;
+	} else if (nval == 2) {
+		bus = false;
+	} else if (!strcmp("apb", apb_bus)) {
+		bus = true;
+	} else if (!strcmp("ahb", apb_bus)) {
+		bus = false;
+	} else {
+		return -EINVAL;
+	}
+
+	return dcc_config_add(drvdata, base, len, bus, curr_list);
+}
+
+static void dcc_config_reset(struct dcc_drvdata *drvdata)
+{
+	struct dcc_config_entry *entry, *temp;
+	int curr_list;
+
+	mutex_lock(&drvdata->mutex);
+
+	for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
+		list_for_each_entry_safe(entry, temp,
+					 &drvdata->cfg_head[curr_list], list) {
+			list_del(&entry->list);
+			kfree(entry);
+		}
+	}
+	drvdata->ram_start = 0;
+	drvdata->ram_cfg = 0;
+	mutex_unlock(&drvdata->mutex);
+}
+
+static ssize_t config_reset_write(struct file *filp,
+				  const char __user *user_buf, size_t count,
+				  loff_t *ppos)
+{
+	unsigned int val, ret;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	ret = kstrtouint_from_user(user_buf, count, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val)
+		dcc_config_reset(drvdata);
+
+	return count;
+}
+
+static const struct file_operations config_reset_fops = {
+	.write = config_reset_write,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static ssize_t ready_read(struct file *filp, char __user *userbuf,
+			  size_t count, loff_t *ppos)
+{
+	int ret = 0;
+	char *buf;
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (!is_dcc_enabled(drvdata)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (!FIELD_GET(BIT(1), readl(drvdata->base + dcc_status(drvdata->mem_map_ver))))
+		buf = "Y\n";
+	else
+		buf = "N\n";
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+
+	if (ret < 0)
+		return -EINVAL;
+	else
+		return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf) + 1);
+}
+
+static const struct file_operations ready_fops = {
+	.read = ready_read,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
+static int dcc_add_loop(struct dcc_drvdata *drvdata, unsigned long loop_cnt, int curr_list)
+{
+	struct dcc_config_entry *entry;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->loop_cnt = min_t(u32, loop_cnt, MAX_LOOP_CNT);
+	entry->desc_type = DCC_LOOP_TYPE;
+	INIT_LIST_HEAD(&entry->list);
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+
+	return 0;
+}
+
+static ssize_t dcc_config_add_loop(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	int ret, i = 0;
+	char *token, *input;
+	char delim[2] = " ";
+	unsigned int val[MAX_LOOP_ADDR];
+
+	input = buf;
+
+	while ((token = strsep(&input, delim)) && i < MAX_LOOP_ADDR) {
+		ret = kstrtoint(token, 0, &val[i++]);
+		if (ret)
+			return ret;
+	}
+
+	if (token) {
+		dev_err(drvdata->dev, "Max limit %u of loop address exceeded",
+			MAX_LOOP_ADDR);
+		return -EINVAL;
+	}
+
+	if (val[1] < 1 || val[1] > 8)
+		return -EINVAL;
+
+	ret = dcc_add_loop(drvdata, val[0], curr_list);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < val[1]; i++)
+		dcc_config_add(drvdata, val[i + 2], 1, false, curr_list);
+
+	return dcc_add_loop(drvdata, 1, curr_list);
+}
+
+static int dcc_rd_mod_wr_add(struct dcc_drvdata *drvdata, unsigned int mask,
+			     unsigned int val, int curr_list)
+{
+	int ret = 0;
+	struct dcc_config_entry *entry;
+
+	mutex_lock(&drvdata->mutex);
+
+	if (list_empty(&drvdata->cfg_head[curr_list])) {
+		dev_err(drvdata->dev, "DCC: No read address programmed\n");
+		ret = -EPERM;
+		goto out_unlock;
+	}
+
+	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
+	if (!entry) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	entry->desc_type = DCC_READ_WRITE_TYPE;
+	entry->mask = mask;
+	entry->write_val = val;
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+out_unlock:
+	mutex_unlock(&drvdata->mutex);
+	return ret;
+}
+
+static ssize_t dcc_config_add_read_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	int ret;
+	int nval;
+	unsigned int addr, mask, val;
+
+	nval = sscanf(buf, "%x %x %x", &addr, &mask, &val);
+
+	if (nval <= 1 || nval > 3)
+		return -EINVAL;
+
+	ret = dcc_config_add(drvdata, addr, 1, false, curr_list);
+	if (ret)
+		return ret;
+
+	return dcc_rd_mod_wr_add(drvdata, mask, val, curr_list);
+}
+
+static int dcc_add_write(struct dcc_drvdata *drvdata, unsigned int addr,
+			 unsigned int write_val, int apb_bus, int curr_list)
+{
+	struct dcc_config_entry *entry;
+
+	entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->desc_type = DCC_WRITE_TYPE;
+	entry->base = addr & GENMASK(31, 4);
+	entry->offset = addr - entry->base;
+	entry->write_val = write_val;
+	entry->len = 1;
+	entry->apb_bus = apb_bus;
+	list_add_tail(&entry->list, &drvdata->cfg_head[curr_list]);
+
+	return 0;
+}
+
+static ssize_t dcc_config_add_write(struct dcc_drvdata *drvdata, char *buf, int curr_list)
+{
+	bool bus;
+	int nval;
+	unsigned int addr, write_val;
+	char apb_bus[4];
+
+	nval = sscanf(buf, "%x %x %3s", &addr, &write_val, apb_bus);
+
+	if (nval <= 1 || nval > 3)
+		return -EINVAL;
+
+	if (nval == 2)
+		bus = true;
+
+	if (nval == 3) {
+		if (!strcmp("apb", apb_bus))
+			bus = true;
+		else if (!strcmp("ahb", apb_bus))
+			bus = false;
+		else
+			return -EINVAL;
+	}
+
+	return dcc_add_write(drvdata, addr, write_val, bus, curr_list);
+}
+
+static int config_show(struct seq_file *m, void *data)
+{
+	struct dcc_drvdata *drvdata = m->private;
+	struct dcc_config_entry *entry;
+	int index = 0, curr_list;
+
+	curr_list = dcc_filp_curr_list(m->file);
+	if (curr_list < 0)
+		return curr_list;
+
+	mutex_lock(&drvdata->mutex);
+
+	list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
+		index++;
+		switch (entry->desc_type) {
+		case DCC_READ_WRITE_TYPE:
+			seq_printf(m, "RW mask: 0x%x, val: 0x%x\n index: 0x%x\n",
+				   entry->mask, entry->write_val, index);
+			break;
+		case DCC_LOOP_TYPE:
+			seq_printf(m, "L index: 0x%x Loop: %d\n", index, entry->loop_cnt);
+			break;
+		case DCC_WRITE_TYPE:
+			seq_printf(m, "W Base:0x%x, Offset: 0x%x, val: 0x%x, APB: %d\n, Index: 0x%x\n",
+				   entry->base, entry->offset, entry->write_val, entry->apb_bus,
+				   index);
+			break;
+		case DCC_READ_TYPE:
+			seq_printf(m, "R Base:0x%x, Offset: 0x%x, len: 0x%x, APB: %d\n, Index: 0x%x\n",
+				   entry->base, entry->offset, entry->len, entry->apb_bus, index);
+		}
+	}
+	mutex_unlock(&drvdata->mutex);
+	return 0;
+}
+
+static int config_open(struct inode *inode, struct file *file)
+{
+	struct dcc_drvdata *drvdata = inode->i_private;
+
+	return single_open(file, config_show, drvdata);
+}
+
+static ssize_t config_write(struct file *filp,
+			    const char __user *user_buf, size_t count,
+			    loff_t *ppos)
+{
+	int ret, curr_list;
+	char *token, buf[50];
+	char *bufp = buf;
+	char *delim = " ";
+	struct dcc_drvdata *drvdata = filp->private_data;
+
+	if (count > sizeof(buf) || count == 0)
+		return -EINVAL;
+
+	ret = copy_from_user(buf, user_buf, count);
+	if (ret)
+		return -EFAULT;
+
+	curr_list = dcc_filp_curr_list(filp);
+	if (curr_list < 0)
+		return curr_list;
+
+	if (buf[count - 1] == '\n')
+		buf[count - 1] = '\0';
+	else
+		return -EINVAL;
+
+	token = strsep(&bufp, delim);
+
+	if (!strcmp("R", token)) {
+		ret = dcc_config_add_read(drvdata, bufp, curr_list);
+	} else if (!strcmp("W", token)) {
+		ret = dcc_config_add_write(drvdata, bufp, curr_list);
+	} else if (!strcmp("RW", token)) {
+		ret = dcc_config_add_read_write(drvdata, bufp, curr_list);
+	} else if (!strcmp("L", token)) {
+		ret = dcc_config_add_loop(drvdata, bufp, curr_list);
+	} else {
+		dev_err(drvdata->dev, "%s is not a correct input\n", token);
+		return -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static const struct file_operations config_fops = {
+	.open = config_open,
+	.read = seq_read,
+	.write = config_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static void dcc_delete_debug_dir(struct dcc_drvdata *drvdata)
+{
+	 debugfs_remove_recursive(drvdata->dbg_dir);
+};
+
+static void dcc_create_debug_dir(struct dcc_drvdata *drvdata)
+{
+	int i;
+	char list_num[10];
+	struct dentry *dcc_dev, *list;
+	struct device *dev = drvdata->dev;
+
+	drvdata->dbg_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
+	dcc_dev = debugfs_create_dir(dev_name(dev), drvdata->dbg_dir);
+
+	for (i = 0; i <= drvdata->nr_link_list; i++) {
+		sprintf(list_num, "%d", i);
+		list = debugfs_create_dir(list_num, dcc_dev);
+		debugfs_create_file("enable", 0600, list, drvdata, &enable_fops);
+		debugfs_create_file("config", 0600, list, drvdata, &config_fops);
+	}
+
+	debugfs_create_file("trigger", 0200, drvdata->dbg_dir, drvdata, &trigger_fops);
+	debugfs_create_file("ready", 0400, drvdata->dbg_dir, drvdata, &ready_fops);
+	debugfs_create_file("config_reset", 0200, drvdata->dbg_dir,
+			    drvdata, &config_reset_fops);
+}
+
+static ssize_t dcc_sram_read(struct file *file, char __user *data,
+			     size_t len, loff_t *ppos)
+{
+	unsigned char *buf;
+	struct dcc_drvdata *drvdata;
+
+	drvdata = container_of(file->private_data, struct dcc_drvdata,
+			       sram_dev);
+
+	/* EOF check */
+	if (*ppos >= drvdata->ram_size)
+		return 0;
+
+	if ((*ppos + len) > drvdata->ram_size)
+		len = (drvdata->ram_size - *ppos);
+
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	memcpy_fromio(buf, drvdata->ram_base + *ppos, len);
+
+	if (copy_to_user(data, buf, len)) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	*ppos += len;
+
+	kfree(buf);
+
+	return len;
+}
+
+static const struct file_operations dcc_sram_fops = {
+	.owner		= THIS_MODULE,
+	.read		= dcc_sram_read,
+	.llseek		= no_llseek,
+};
+
+static int dcc_sram_dev_init(struct dcc_drvdata *drvdata)
+{
+	drvdata->sram_dev.minor = MISC_DYNAMIC_MINOR;
+	drvdata->sram_dev.name = "dcc_sram";
+	drvdata->sram_dev.fops = &dcc_sram_fops;
+
+	return misc_register(&drvdata->sram_dev);
+}
+
+static void dcc_sram_dev_exit(struct dcc_drvdata *drvdata)
+{
+	misc_deregister(&drvdata->sram_dev);
+}
+
+static int dcc_probe(struct platform_device *pdev)
+{
+	u32 val;
+	int ret = 0, i;
+	struct device *dev = &pdev->dev;
+	struct dcc_drvdata *drvdata;
+	struct resource *res;
+
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	drvdata->dev = &pdev->dev;
+	platform_set_drvdata(pdev, drvdata);
+
+	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(drvdata->base))
+		return PTR_ERR(drvdata->base);
+
+	drvdata->ram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
+	if (IS_ERR(drvdata->ram_base))
+		return PTR_ERR(drvdata->ram_base);
+
+	drvdata->ram_size = resource_size(res);
+
+	drvdata->ram_offset = (size_t)of_device_get_match_data(&pdev->dev);
+
+	val = readl(drvdata->base + DCC_HW_INFO);
+
+	if (FIELD_GET(DCC_VER_INFO_MASK, val)) {
+		drvdata->mem_map_ver = 3;
+		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
+		if (!drvdata->nr_link_list)
+			return	-EINVAL;
+	} else if ((val & DCC_VER_MASK2) == DCC_VER_MASK2) {
+		drvdata->mem_map_ver = 2;
+		drvdata->nr_link_list = readl(drvdata->base + DCC_LL_NUM_INFO);
+		if (!drvdata->nr_link_list)
+			return	-EINVAL;
+	} else {
+		drvdata->mem_map_ver = 1;
+		drvdata->nr_link_list = DCC_MAX_LINK_LIST;
+	}
+
+	/* Either set the fixed loop offset or calculate
+	 * it from the total number of words in dcc_sram.
+	 * Max consecutive addresses dcc can loop is
+	 * equivalent to the words in dcc_sram.
+	 */
+	if (val & DCC_LOOP_OFFSET_MASK)
+		drvdata->loop_shift = DCC_FIX_LOOP_OFFSET;
+	else
+		drvdata->loop_shift = get_bitmask_order((drvdata->ram_offset +
+					drvdata->ram_size) / DCC_SRAM_WORD_LENGTH - 1);
+
+	mutex_init(&drvdata->mutex);
+
+	drvdata->enable_bitmap = devm_kcalloc(dev, BITS_TO_LONGS(drvdata->nr_link_list),
+					      sizeof(*drvdata->enable_bitmap), GFP_KERNEL);
+	if (!drvdata->enable_bitmap)
+		return -ENOMEM;
+
+	drvdata->cfg_head = devm_kcalloc(dev, drvdata->nr_link_list,
+					 sizeof(*drvdata->cfg_head), GFP_KERNEL);
+	if (!drvdata->cfg_head)
+		return -ENOMEM;
+
+	for (i = 0; i < drvdata->nr_link_list; i++)
+		INIT_LIST_HEAD(&drvdata->cfg_head[i]);
+
+	ret = dcc_sram_dev_init(drvdata);
+	if (ret) {
+		dev_err(drvdata->dev, "DCC: sram node not registered.\n");
+		return ret;
+	}
+
+	dcc_create_debug_dir(drvdata);
+
+	return 0;
+}
+
+static int dcc_remove(struct platform_device *pdev)
+{
+	struct dcc_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	dcc_delete_debug_dir(drvdata);
+	dcc_sram_dev_exit(drvdata);
+	dcc_config_reset(drvdata);
+
+	return 0;
+}
+
+static const struct of_device_id dcc_match_table[] = {
+	{ .compatible = "qcom,sc7180-dcc", .data = (void *)0x6000 },
+	{ .compatible = "qcom,sc7280-dcc", .data = (void *)0x12000 },
+	{ .compatible = "qcom,sdm845-dcc", .data = (void *)0x6000 },
+	{ .compatible = "qcom,sm8150-dcc", .data = (void *)0x5000 },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dcc_match_table);
+
+static struct platform_driver dcc_driver = {
+	.probe = dcc_probe,
+	.remove	= dcc_remove,
+	.driver	= {
+		.name = "qcom-dcc",
+		.of_match_table	= dcc_match_table,
+	},
+};
+
+module_platform_driver(dcc_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Qualcomm Technologies Inc. DCC driver");
+