[v3,2/3] pwm: Add Aspeed ast2600 PWM support

Commit Message

Billy Tsai Nov. 2, 2022, 8:36 a.m. UTC

This patch add the support of PWM controller which can be found at aspeed
ast2600 soc. The pwm supoorts up to 16 channels and it's part function
of multi-function device "pwm-tach controller".

Signed-off-by: Billy Tsai <[e-mail]>
Reviewed-by: Uwe Kleine-König <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
---
 drivers/pwm/Kconfig              |  10 +
 drivers/pwm/Makefile             |   1 +
 drivers/pwm/pwm-aspeed-ast2600.c | 319 +++++++++++++++++++++++++++++++
 3 files changed, 330 insertions(+)
 create mode 100644 drivers/pwm/pwm-aspeed-ast2600.c

Comments

Biju Das Nov. 2, 2022, 3:56 p.m. UTC | #1

Hi Billy Tsai,

Thanks for the patch.

> Subject: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> 
> This patch add the support of PWM controller which can be found at
> aspeed
> ast2600 soc. The pwm supoorts up to 16 channels and it's part function
> of multi-function device "pwm-tach controller".
> 
> Signed-off-by: Billy Tsai <[e-mail]>
> Reviewed-by: Uwe Kleine-König <[e-mail]>
> Reported-by: kernel test robot <[e-mail]>
> ---
>  drivers/pwm/Kconfig              |  10 +
>  drivers/pwm/Makefile             |   1 +
>  drivers/pwm/pwm-aspeed-ast2600.c | 319
> +++++++++++++++++++++++++++++++
>  3 files changed, 330 insertions(+)
>  create mode 100644 drivers/pwm/pwm-aspeed-ast2600.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index
> aa29841bbb79..3313f074f15e 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -51,6 +51,16 @@ config PWM_AB8500
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-ab8500.
> 
> +config PWM_ASPEED_AST2600
> +	tristate "Aspeed ast2600 PWM support"
> +	depends on ARCH_ASPEED || COMPILE_TEST
> +	depends on HAVE_CLK && HAS_IOMEM
> +	help
> +	  This driver provides support for Aspeed ast2600 PWM
> controllers.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-aspeed-ast2600.
> +
>  config PWM_ATMEL
>  	tristate "Atmel PWM support"
>  	depends on ARCH_AT91 || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index
> 708840b7fba8..6be0c67bf08a 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_PWM)		+= core.o
>  obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
>  obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
> +obj-$(CONFIG_PWM_ASPEED_AST2600)	+= pwm-aspeed-ast2600.o
>  obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
>  obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
>  obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
> diff --git a/drivers/pwm/pwm-aspeed-ast2600.c b/drivers/pwm/pwm-
> aspeed-ast2600.c
> new file mode 100644
> index 000000000000..e571e9fadf0f
> --- /dev/null
> +++ b/drivers/pwm/pwm-aspeed-ast2600.c
> @@ -0,0 +1,319 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2021 Aspeed Technology Inc.
> + *
> + * PWM controller driver for Aspeed ast2600 SoCs.
> + * This drivers doesn't support earlier version of the IP.
> + *
> + * The hardware operates in time quantities of length
> + * Q := (DIV_L + 1) << DIV_H / input-clk
> + * The length of a PWM period is (DUTY_CYCLE_PERIOD + 1) * Q.
> + * The maximal value for DUTY_CYCLE_PERIOD is used here to provide
> + * a fine grained selection for the duty cycle.
> + *
> + * This driver uses DUTY_CYCLE_RISING_POINT = 0, so from the start of
> a
> + * period the output is active until DUTY_CYCLE_FALLING_POINT * Q.
> Note
> + * that if DUTY_CYCLE_RISING_POINT = DUTY_CYCLE_FALLING_POINT the
> +output is
> + * always active.
> + *
> + * Register usage:
> + * PIN_ENABLE: When it is unset the pwm controller will emit inactive
> level to the external.
> + * Use to determine whether the PWM channel is enabled or disabled
> + * CLK_ENABLE: When it is unset the pwm controller will assert the
> duty
> +counter reset and
> + * emit inactive level to the PIN_ENABLE mux after that the driver
> can
> +still change the pwm period
> + * and duty and the value will apply when CLK_ENABLE be set again.
> + * Use to determine whether duty_cycle bigger than 0.
> + * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will
> inverse immediately.
> + *
> +PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POIN
> T:
> +When these two
> + * values are equal it means the duty cycle = 100%.
> + *
> + * The glitch may generate at:
> + * - Enabled changing when the duty_cycle bigger than 0% and less
> than 100%.
> + * - Polarity changing when the duty_cycle bigger than 0% and less
> than 100%.
> + *
> + * Limitations:
> + * - When changing both duty cycle and period, we cannot prevent in
> + *   software that the output might produce a period with mixed
> + *   settings.
> + * - Disabling the PWM doesn't complete the current period.
> + *
> + * Improvements:
> + * - When only changing one of duty cycle or period, our pwm
> controller will not
> + *   generate the glitch, the configure will change at next cycle of
> pwm.
> + *   This improvement can disable/enable through
> PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/errno.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/math64.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>

Do you need all the includes?

> +#include <linux/sysfs.h>


> +
> +/* The channel number of Aspeed pwm controller */
> +#define PWM_ASPEED_NR_PWMS			16
> +/* PWM Control Register */
> +#define PWM_ASPEED_CTRL(ch)			((ch) * 0x10 + 0x00)
> +#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT	BIT(19)
> +#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE	BIT(18)
> +#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE	BIT(17)
> +#define PWM_ASPEED_CTRL_CLK_ENABLE		BIT(16)
> +#define PWM_ASPEED_CTRL_LEVEL_OUTPUT		BIT(15)
> +#define PWM_ASPEED_CTRL_INVERSE			BIT(14)
> +#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE	BIT(13)
> +#define PWM_ASPEED_CTRL_PIN_ENABLE		BIT(12)
> +#define PWM_ASPEED_CTRL_CLK_DIV_H		GENMASK(11, 8)
> +#define PWM_ASPEED_CTRL_CLK_DIV_L		GENMASK(7, 0)
> +
> +/* PWM Duty Cycle Register */
> +#define PWM_ASPEED_DUTY_CYCLE(ch)		((ch) * 0x10 + 0x04)
> +#define PWM_ASPEED_DUTY_CYCLE_PERIOD		GENMASK(31, 24)
> +#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT	GENMASK(23, 16)
> +#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT	GENMASK(15, 8)
> +#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT	GENMASK(7, 0)
> +
> +/* PWM fixed value */
> +#define PWM_ASPEED_FIXED_PERIOD
> 	FIELD_MAX(PWM_ASPEED_DUTY_CYCLE_PERIOD)
> +
> +struct aspeed_pwm_data {
> +	struct pwm_chip chip;
> +	struct clk *clk;
> +	struct regmap *regmap;
> +	struct reset_control *reset;
> +};
> +
> +static inline struct aspeed_pwm_data *
> +aspeed_pwm_chip_to_data(struct pwm_chip *chip) {
> +	return container_of(chip, struct aspeed_pwm_data, chip); }
> +
> +static void aspeed_pwm_get_state(struct pwm_chip *chip, struct
> pwm_device *pwm,
> +				 struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	u32 hwpwm = pwm->hwpwm;
> +	bool polarity,	pin_en, clk_en;
> +	u32 duty_pt, val;
> +	unsigned long rate;
> +	u64 div_h, div_l, duty_cycle_period, dividend;
> +
> +	regmap_read(priv->regmap, PWM_ASPEED_CTRL(hwpwm), &val);
> +	polarity = FIELD_GET(PWM_ASPEED_CTRL_INVERSE, val);
> +	pin_en = FIELD_GET(PWM_ASPEED_CTRL_PIN_ENABLE, val);
> +	clk_en = FIELD_GET(PWM_ASPEED_CTRL_CLK_ENABLE, val);
> +	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
> +	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
> +	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE(hwpwm), &val);
> +	duty_pt = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, val);
> +	duty_cycle_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
> +
> +	rate = clk_get_rate(priv->clk);
> +
> +	/*
> +	 * This multiplication doesn't overflow, the upper bound is
> +	 * 1000000000 * 256 * 256 << 15 = 0x1dcd650000000000
> +	 */
> +	dividend = (u64)NSEC_PER_SEC * (div_l + 1) * (duty_cycle_period +
> 1)
> +		       << div_h;
> +	state->period = DIV_ROUND_UP_ULL(dividend, rate);
> +
> +	if (clk_en && duty_pt) {
> +		dividend = (u64)NSEC_PER_SEC * (div_l + 1) * duty_pt
> +				 << div_h;
> +		state->duty_cycle = DIV_ROUND_UP_ULL(dividend, rate);
> +	} else {
> +		state->duty_cycle = clk_en ? state->period : 0;
> +	}
> +	state->polarity = polarity ? PWM_POLARITY_INVERSED :
> PWM_POLARITY_NORMAL;
> +	state->enabled = pin_en;
> +	dev_dbg(dev, "get period: %lldns, duty_cycle: %lldns", state-
> >period,
> +		state->duty_cycle);
> +}
> +
> +static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device
> *pwm,
> +			    const struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	u32 hwpwm = pwm->hwpwm, duty_pt;
> +	unsigned long rate;
> +	u64 div_h, div_l, divisor, expect_period;
> +	bool clk_en;
> +
> +	rate = clk_get_rate(priv->clk);
> +	expect_period = min(div64_u64(ULLONG_MAX, (u64)rate), state-
> >period);
> +	dev_dbg(dev, "expect period: %lldns, duty_cycle: %lldns",
> expect_period,
> +		state->duty_cycle);
> +	/*
> +	 * Pick the smallest value for div_h so that div_l can be the
> biggest
> +	 * which results in a finer resolution near the target period
> value.
> +	 */
> +	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
> +		  (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1);
> +	div_h = order_base_2(DIV64_U64_ROUND_UP(rate * expect_period,
> divisor));
> +	if (div_h > 0xf)
> +		div_h = 0xf;
> +
> +	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) <<
> div_h;
> +	div_l = div64_u64(rate * expect_period, divisor);
> +
> +	if (div_l == 0)
> +		return -ERANGE;
> +
> +	div_l -= 1;
> +
> +	if (div_l > 255)
> +		div_l = 255;
> +
> +	dev_dbg(dev, "clk source: %ld div_h %lld, div_l : %lld\n", rate,
> div_h,
> +		div_l);
> +	/* duty_pt = duty_cycle * (PERIOD + 1) / period */
> +	duty_pt = div64_u64(state->duty_cycle * rate,
> +			    (u64)NSEC_PER_SEC * (div_l + 1) << div_h);
> +	dev_dbg(dev, "duty_cycle = %lld, duty_pt = %d\n", state-
> >duty_cycle,
> +		duty_pt);
> +
> +	/*
> +	 * Fixed DUTY_CYCLE_PERIOD to its max value to get a
> +	 * fine-grained resolution for duty_cycle at the expense of a
> +	 * coarser period resolution.
> +	 */
> +	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE(hwpwm),
> +			   PWM_ASPEED_DUTY_CYCLE_PERIOD,
> +			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
> +				      PWM_ASPEED_FIXED_PERIOD));
> +	if (duty_pt == 0) {
> +		/* emit inactive level and assert the duty counter reset */
> +		clk_en = 0;
> +	} else {
> +		clk_en = 1;
> +		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
> +			duty_pt = 0;
> +		regmap_update_bits(priv->regmap,
> PWM_ASPEED_DUTY_CYCLE(hwpwm),
> +				   PWM_ASPEED_DUTY_CYCLE_RISING_POINT |
> +					   PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
> +
> FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, duty_pt));
> +	}
> +
> +	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL(hwpwm),
> +			   PWM_ASPEED_CTRL_CLK_DIV_H |
> PWM_ASPEED_CTRL_CLK_DIV_L |
> +				   PWM_ASPEED_CTRL_PIN_ENABLE |
> PWM_ASPEED_CTRL_CLK_ENABLE |
> +				   PWM_ASPEED_CTRL_INVERSE,
> +			   FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
> +				   FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l)
> |
> +				   FIELD_PREP(PWM_ASPEED_CTRL_PIN_ENABLE,
> state->enabled) |
> +				   FIELD_PREP(PWM_ASPEED_CTRL_CLK_ENABLE,
> clk_en) |
> +				   FIELD_PREP(PWM_ASPEED_CTRL_INVERSE, state-
> >polarity));
> +	return 0;
> +}
> +
> +static const struct pwm_ops aspeed_pwm_ops = {
> +	.apply = aspeed_pwm_apply,
> +	.get_state = aspeed_pwm_get_state,
> +	.owner = THIS_MODULE,
> +};
> +
> +static void aspeed_pwm_reset_assert(void *data) {
> +	struct reset_control *rst = data;
> +
> +	reset_control_assert(rst);
> +}
> +
> +static void aspeed_pwm_chip_remove(void *data) {
> +	struct pwm_chip *chip = data;
> +
> +	pwmchip_remove(chip);
> +}
> +
> +static int aspeed_pwm_probe(struct platform_device *pdev) {
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +	struct aspeed_pwm_data *priv;
> +	struct device_node *np;
> +	struct platform_device *parent_dev;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	np = pdev->dev.parent->of_node;
> +	if (!of_device_is_compatible(np, "aspeed,ast2600-pwm-tach"))
> +		return dev_err_probe(dev, -ENODEV,
> +				     "Unsupported pwm device binding\n");
> +
> +	priv->regmap = syscon_node_to_regmap(np);
> +	if (IS_ERR(priv->regmap))
> +		return dev_err_probe(dev, PTR_ERR(priv->regmap),
> +				     "Couldn't get regmap\n");
> +
> +	parent_dev = of_find_device_by_node(np);
> +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> +				     "Couldn't get clock\n");

What is the use case?

Is pwm configured by boot loader initially ?

Or

pwm configured by Linux, not by the bootloader initially?

Or

Driver needs to handle both cases?

Just asking, because you are turning on the clock unnecessarily here,
If you need to address all the use cases. If it is just first one, then
It is ok.


Cheers,
Biju

> +
> +	priv->reset = devm_reset_control_get_shared(&parent_dev->dev,
> NULL);
> +	if (IS_ERR(priv->reset))
> +		return dev_err_probe(dev, PTR_ERR(priv->reset),
> +				     "Couldn't get reset control\n");
> +
> +	ret = reset_control_deassert(priv->reset);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Couldn't deassert reset control\n");
> +
> +	ret = devm_add_action_or_reset(dev, aspeed_pwm_reset_assert,
> +				       priv->reset);
> +	if (ret)
> +		return ret;
> +
> +	priv->chip.dev = dev;
> +	priv->chip.ops = &aspeed_pwm_ops;
> +	priv->chip.npwm = PWM_ASPEED_NR_PWMS;
> +
> +	ret = pwmchip_add(&priv->chip);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
> +	ret = devm_add_action_or_reset(dev, aspeed_pwm_chip_remove,
> +				       &priv->chip);
> +	if (ret)
> +		return ret;
> +	return 0;
> +}
> +
> +static const struct of_device_id of_pwm_match_table[] = {
> +	{
> +		.compatible = "aspeed,ast2600-pwm",
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, of_pwm_match_table);
> +
> +static struct platform_driver aspeed_pwm_driver = {
> +	.probe = aspeed_pwm_probe,
> +	.driver	= {
> +		.name = "aspeed-pwm",
> +		.of_match_table = of_pwm_match_table,
> +	},
> +};
> +
> +module_platform_driver(aspeed_pwm_driver);
> +
> +MODULE_AUTHOR("Billy Tsai <[e-mail]>");
> +MODULE_DESCRIPTION("Aspeed ast2600 PWM device driver");
> +MODULE_LICENSE("GPL v2");
> --

Billy Tsai Nov. 7, 2022, 8:47 a.m. UTC | #2

On 2022/11/2, 11:56 PM, "Biju Das" <[e-mail]> wrote:

    > > +	parent_dev = of_find_device_by_node(np);
    > > +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
    > > +	if (IS_ERR(priv->clk))
    > > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
    > > +				     "Couldn't get clock\n");

    > What is the use case?

    > Is pwm configured by boot loader initially ?

    > Or

    > pwm configured by Linux, not by the bootloader initially?

    > Or

    > Driver needs to handle both cases?

    > Just asking, because you are turning on the clock unnecessarily here,
    > If you need to address all the use cases. If it is just first one, then
    > It is ok.

Hi Biju,

The driver want to handle all of the use cases. Can you tell me why turning on the clock
is unnecessarily here?

Thanks

Best Regards,
Billy Tsai

Biju Das Nov. 7, 2022, 8:55 a.m. UTC | #3

Hi Billy Tsai,

> -----Original Message-----
> From: Billy Tsai <[e-mail]>
> Sent: 07 November 2022 08:48
> To: Biju Das <[e-mail]>; [e-mail]; linux@roeck-
> us.net; [e-mail]; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; u.kleine-
> [e-mail]; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; linux-
> [e-mail]; [e-mail]; linux-
> [e-mail]; BMC-SW <[e-mail]>; [e-mail]
> Cc: kernel test robot <[e-mail]>
> Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> 
> On 2022/11/2, 11:56 PM, "Biju Das" <[e-mail]> wrote:
> 
>     > > +	parent_dev = of_find_device_by_node(np);
>     > > +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
>     > > +	if (IS_ERR(priv->clk))
>     > > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
>     > > +				     "Couldn't get clock\n");
> 
>     > What is the use case?
> 
>     > Is pwm configured by boot loader initially ?
> 
>     > Or
> 
>     > pwm configured by Linux, not by the bootloader initially?
> 
>     > Or
> 
>     > Driver needs to handle both cases?
> 
>     > Just asking, because you are turning on the clock unnecessarily here,
>     > If you need to address all the use cases. If it is just first one, then
>     > It is ok.
> 
> Hi Biju,
> 
> The driver want to handle all of the use cases. Can you tell me why turning
> on the clock is unnecessarily here?

For the use case, "pwm configured by Linux, not by the bootloader initially",

You are unnecessarily turning on the clocks. You could 

enable it during pwm_enable
and disable it during pwm_disable.

For configuring registers, while pwm is in disable state, 
you could just turn on the clock and do the register configurations and turn it off.

By this way you are saving power.

Cheers,
Biju

Billy Tsai Nov. 7, 2022, 9:25 a.m. UTC | #4

On 2022/11/7, 4:55 PM, "Biju Das" <[e-mail]> wrote:

    > > -----Original Message-----
    > > From: Billy Tsai <[e-mail]>
    > > Sent: 07 November 2022 08:48
    > > To: Biju Das <[e-mail]>; [e-mail]; linux@roeck-
    > > us.net; [e-mail]; [e-mail]; [e-mail];
    > > [e-mail]; [e-mail]; u.kleine-
    > > [e-mail]; [e-mail]; [e-mail];
    > > [e-mail]; [e-mail]; linux-
    > > [e-mail]; [e-mail]; linux-
    > > [e-mail]; BMC-SW <[e-mail]>; [e-mail]
    > > Cc: kernel test robot <[e-mail]>
    > > Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
    > > 
    > > On 2022/11/2, 11:56 PM, "Biju Das" <[e-mail]> wrote:
    > > 
    > >     > > +	parent_dev = of_find_device_by_node(np);
    > >     > > +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
    > >     > > +	if (IS_ERR(priv->clk))
    > >     > > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
    > >     > > +				     "Couldn't get clock\n");
    > > 
    > >     > What is the use case?
    > > 
    > >     > Is pwm configured by boot loader initially ?
    > > 
    > >     > Or
    > > 
    > >     > pwm configured by Linux, not by the bootloader initially?
    > > 
    > >     > Or
    > > 
    > >     > Driver needs to handle both cases?
    > > 
    > >     > Just asking, because you are turning on the clock unnecessarily here,
    > >     > If you need to address all the use cases. If it is just first one, then
    > >     > It is ok.
    > > 
    > > Hi Biju,
    > > 
    > > The driver want to handle all of the use cases. Can you tell me why turning
    > > on the clock is unnecessarily here?

    > For the use case, "pwm configured by Linux, not by the bootloader initially",

    > You are unnecessarily turning on the clocks. You could 

    > enable it during pwm_enable
    > and disable it during pwm_disable.

    > For configuring registers, while pwm is in disable state, 
    > you could just turn on the clock and do the register configurations and turn it off.

    > By this way you are saving power.

Hi Biju,

This clock is the source clock for the pwm controller (include the accessing for the register).
For the output of the PWM (pwm_enable/pwm_disable), the controller have another register to control it.

Best Regards,
Billy Tsai

Biju Das Nov. 7, 2022, 9:31 a.m. UTC | #5

Hi Billy Tsai,

> -----Original Message-----
> From: Billy Tsai <[e-mail]>
> Sent: 07 November 2022 09:26
> To: Biju Das <[e-mail]>; [e-mail]; linux@roeck-
> us.net; [e-mail]; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; u.kleine-
> [e-mail]; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; linux-
> [e-mail]; [e-mail]; linux-
> [e-mail]; BMC-SW <[e-mail]>; [e-mail]
> Cc: kernel test robot <[e-mail]>; Geert Uytterhoeven
> <[e-mail]>
> Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> 
> On 2022/11/7, 4:55 PM, "Biju Das" <[e-mail]> wrote:
> 
>     > > -----Original Message-----
>     > > From: Billy Tsai <[e-mail]>
>     > > Sent: 07 November 2022 08:48
>     > > To: Biju Das <[e-mail]>; [e-mail];
> linux@roeck-
>     > > us.net; [e-mail]; [e-mail]; [e-mail];
>     > > [e-mail]; [e-mail]; u.kleine-
>     > > [e-mail]; [e-mail]; linux-
> [e-mail];
>     > > [e-mail]; [e-mail];
> linux-
>     > > [e-mail]; [e-mail]; linux-
>     > > [e-mail]; BMC-SW <[e-mail]>;
> [e-mail]
>     > > Cc: kernel test robot <[e-mail]>
>     > > Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
>     > >
>     > > On 2022/11/2, 11:56 PM, "Biju Das" <[e-mail]>
> wrote:
>     > >
>     > >     > > +	parent_dev = of_find_device_by_node(np);
>     > >     > > +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
>     > >     > > +	if (IS_ERR(priv->clk))
>     > >     > > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
>     > >     > > +				     "Couldn't get clock\n");
>     > >
>     > >     > What is the use case?
>     > >
>     > >     > Is pwm configured by boot loader initially ?
>     > >
>     > >     > Or
>     > >
>     > >     > pwm configured by Linux, not by the bootloader initially?
>     > >
>     > >     > Or
>     > >
>     > >     > Driver needs to handle both cases?
>     > >
>     > >     > Just asking, because you are turning on the clock unnecessarily
> here,
>     > >     > If you need to address all the use cases. If it is just first
> one, then
>     > >     > It is ok.
>     > >
>     > > Hi Biju,
>     > >
>     > > The driver want to handle all of the use cases. Can you tell me why
> turning
>     > > on the clock is unnecessarily here?
> 
>     > For the use case, "pwm configured by Linux, not by the bootloader
> initially",
> 
>     > You are unnecessarily turning on the clocks. You could
> 
>     > enable it during pwm_enable
>     > and disable it during pwm_disable.
> 
>     > For configuring registers, while pwm is in disable state,
>     > you could just turn on the clock and do the register configurations and
> turn it off.
> 
>     > By this way you are saving power.
> 
> Hi Biju,
> 
> This clock is the source clock for the pwm controller (include the accessing
> for the register).

OK, But the driver has only one clock (priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL)).
You are always turning it on during probe.


> For the output of the PWM (pwm_enable/pwm_disable), the controller have
> another register to control it.

That is enable/disable register for controlling the output of PWM.

Cheers,
Biju

Biju Das Nov. 7, 2022, 9:38 a.m. UTC | #6

> Subject: RE: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> 
> Hi Billy Tsai,
> 
> > -----Original Message-----
> > From: Billy Tsai <[e-mail]>
> > Sent: 07 November 2022 09:26
> > To: Biju Das <[e-mail]>; [e-mail];
> > linux@roeck- us.net; [e-mail]; [e-mail];
> > [e-mail]; [e-mail]; [e-mail];
> > u.kleine- [e-mail]; [e-mail];
> > [e-mail]; [e-mail];
> > [e-mail]; linux- [e-mail];
> > [e-mail]; linux- [e-mail]; BMC-SW
> > <[e-mail]>; [e-mail]
> > Cc: kernel test robot <[e-mail]>; Geert Uytterhoeven
> > <[e-mail]>
> > Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> >
> > On 2022/11/7, 4:55 PM, "Biju Das" <[e-mail]> wrote:
> >
> >     > > -----Original Message-----
> >     > > From: Billy Tsai <[e-mail]>
> >     > > Sent: 07 November 2022 08:48
> >     > > To: Biju Das <[e-mail]>; [e-mail];
> > linux@roeck-
> >     > > us.net; [e-mail]; [e-mail]; [e-mail];
> >     > > [e-mail]; [e-mail]; u.kleine-
> >     > > [e-mail]; [e-mail]; linux-
> > [e-mail];
> >     > > [e-mail];
> > [e-mail];
> > linux-
> >     > > [e-mail]; [e-mail]; linux-
> >     > > [e-mail]; BMC-SW <[e-mail]>;
> > [e-mail]
> >     > > Cc: kernel test robot <[e-mail]>
> >     > > Subject: Re: [v3 2/3] pwm: Add Aspeed ast2600 PWM support
> >     > >
> >     > > On 2022/11/2, 11:56 PM, "Biju Das"
> > <[e-mail]>
> > wrote:
> >     > >
> >     > >     > > +	parent_dev = of_find_device_by_node(np);
> >     > >     > > +	priv->clk = devm_clk_get_enabled(&parent_dev->dev,
> NULL);
> >     > >     > > +	if (IS_ERR(priv->clk))
> >     > >     > > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> >     > >     > > +				     "Couldn't get clock\n");
> >     > >
> >     > >     > What is the use case?
> >     > >
> >     > >     > Is pwm configured by boot loader initially ?
> >     > >
> >     > >     > Or
> >     > >
> >     > >     > pwm configured by Linux, not by the bootloader initially?
> >     > >
> >     > >     > Or
> >     > >
> >     > >     > Driver needs to handle both cases?
> >     > >
> >     > >     > Just asking, because you are turning on the clock
> unnecessarily
> > here,
> >     > >     > If you need to address all the use cases. If it is just first
> > one, then
> >     > >     > It is ok.
> >     > >
> >     > > Hi Biju,
> >     > >
> >     > > The driver want to handle all of the use cases. Can you tell
> > me why turning
> >     > > on the clock is unnecessarily here?
> >
> >     > For the use case, "pwm configured by Linux, not by the
> > bootloader initially",
> >
> >     > You are unnecessarily turning on the clocks. You could
> >
> >     > enable it during pwm_enable
> >     > and disable it during pwm_disable.
> >
> >     > For configuring registers, while pwm is in disable state,
> >     > you could just turn on the clock and do the register
> > configurations and turn it off.
> >
> >     > By this way you are saving power.
> >
> > Hi Biju,
> >
> > This clock is the source clock for the pwm controller (include the
> > accessing for the register).
> 
> OK, But the driver has only one clock (priv->clk =
> devm_clk_get_enabled(&parent_dev->dev, NULL)).
> You are always turning it on during probe.

Your system needs this clock always on, then it is OK.

Cheers,
Biju

Patch

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index aa29841bbb79..3313f074f15e 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -51,6 +51,16 @@  config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_ASPEED_AST2600
+	tristate "Aspeed ast2600 PWM support"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	depends on HAVE_CLK && HAS_IOMEM
+	help
+	  This driver provides support for Aspeed ast2600 PWM controllers.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-aspeed-ast2600.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on ARCH_AT91 || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 708840b7fba8..6be0c67bf08a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -2,6 +2,7 @@ 
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_ASPEED_AST2600)	+= pwm-aspeed-ast2600.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-aspeed-ast2600.c b/drivers/pwm/pwm-aspeed-ast2600.c
new file mode 100644
index 000000000000..e571e9fadf0f
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed-ast2600.c
@@ -0,0 +1,319 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2021 Aspeed Technology Inc.
+ *
+ * PWM controller driver for Aspeed ast2600 SoCs.
+ * This drivers doesn't support earlier version of the IP.
+ *
+ * The hardware operates in time quantities of length
+ * Q := (DIV_L + 1) << DIV_H / input-clk
+ * The length of a PWM period is (DUTY_CYCLE_PERIOD + 1) * Q.
+ * The maximal value for DUTY_CYCLE_PERIOD is used here to provide
+ * a fine grained selection for the duty cycle.
+ *
+ * This driver uses DUTY_CYCLE_RISING_POINT = 0, so from the start of a
+ * period the output is active until DUTY_CYCLE_FALLING_POINT * Q. Note
+ * that if DUTY_CYCLE_RISING_POINT = DUTY_CYCLE_FALLING_POINT the output is
+ * always active.
+ *
+ * Register usage:
+ * PIN_ENABLE: When it is unset the pwm controller will emit inactive level to the external.
+ * Use to determine whether the PWM channel is enabled or disabled
+ * CLK_ENABLE: When it is unset the pwm controller will assert the duty counter reset and
+ * emit inactive level to the PIN_ENABLE mux after that the driver can still change the pwm period
+ * and duty and the value will apply when CLK_ENABLE be set again.
+ * Use to determine whether duty_cycle bigger than 0.
+ * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will inverse immediately.
+ * PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POINT: When these two
+ * values are equal it means the duty cycle = 100%.
+ *
+ * The glitch may generate at:
+ * - Enabled changing when the duty_cycle bigger than 0% and less than 100%.
+ * - Polarity changing when the duty_cycle bigger than 0% and less than 100%.
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings.
+ * - Disabling the PWM doesn't complete the current period.
+ *
+ * Improvements:
+ * - When only changing one of duty cycle or period, our pwm controller will not
+ *   generate the glitch, the configure will change at next cycle of pwm.
+ *   This improvement can disable/enable through PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+/* The channel number of Aspeed pwm controller */
+#define PWM_ASPEED_NR_PWMS			16
+/* PWM Control Register */
+#define PWM_ASPEED_CTRL(ch)			((ch) * 0x10 + 0x00)
+#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT	BIT(19)
+#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE	BIT(18)
+#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE	BIT(17)
+#define PWM_ASPEED_CTRL_CLK_ENABLE		BIT(16)
+#define PWM_ASPEED_CTRL_LEVEL_OUTPUT		BIT(15)
+#define PWM_ASPEED_CTRL_INVERSE			BIT(14)
+#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE	BIT(13)
+#define PWM_ASPEED_CTRL_PIN_ENABLE		BIT(12)
+#define PWM_ASPEED_CTRL_CLK_DIV_H		GENMASK(11, 8)
+#define PWM_ASPEED_CTRL_CLK_DIV_L		GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE(ch)		((ch) * 0x10 + 0x04)
+#define PWM_ASPEED_DUTY_CYCLE_PERIOD		GENMASK(31, 24)
+#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT	GENMASK(23, 16)
+#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT	GENMASK(15, 8)
+#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT	GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_ASPEED_FIXED_PERIOD			FIELD_MAX(PWM_ASPEED_DUTY_CYCLE_PERIOD)
+
+struct aspeed_pwm_data {
+	struct pwm_chip chip;
+	struct clk *clk;
+	struct regmap *regmap;
+	struct reset_control *reset;
+};
+
+static inline struct aspeed_pwm_data *
+aspeed_pwm_chip_to_data(struct pwm_chip *chip)
+{
+	return container_of(chip, struct aspeed_pwm_data, chip);
+}
+
+static void aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 hwpwm = pwm->hwpwm;
+	bool polarity,	pin_en, clk_en;
+	u32 duty_pt, val;
+	unsigned long rate;
+	u64 div_h, div_l, duty_cycle_period, dividend;
+
+	regmap_read(priv->regmap, PWM_ASPEED_CTRL(hwpwm), &val);
+	polarity = FIELD_GET(PWM_ASPEED_CTRL_INVERSE, val);
+	pin_en = FIELD_GET(PWM_ASPEED_CTRL_PIN_ENABLE, val);
+	clk_en = FIELD_GET(PWM_ASPEED_CTRL_CLK_ENABLE, val);
+	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
+	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
+	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE(hwpwm), &val);
+	duty_pt = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, val);
+	duty_cycle_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
+
+	rate = clk_get_rate(priv->clk);
+
+	/*
+	 * This multiplication doesn't overflow, the upper bound is
+	 * 1000000000 * 256 * 256 << 15 = 0x1dcd650000000000
+	 */
+	dividend = (u64)NSEC_PER_SEC * (div_l + 1) * (duty_cycle_period + 1)
+		       << div_h;
+	state->period = DIV_ROUND_UP_ULL(dividend, rate);
+
+	if (clk_en && duty_pt) {
+		dividend = (u64)NSEC_PER_SEC * (div_l + 1) * duty_pt
+				 << div_h;
+		state->duty_cycle = DIV_ROUND_UP_ULL(dividend, rate);
+	} else {
+		state->duty_cycle = clk_en ? state->period : 0;
+	}
+	state->polarity = polarity ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
+	state->enabled = pin_en;
+	dev_dbg(dev, "get period: %lldns, duty_cycle: %lldns", state->period,
+		state->duty_cycle);
+}
+
+static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 hwpwm = pwm->hwpwm, duty_pt;
+	unsigned long rate;
+	u64 div_h, div_l, divisor, expect_period;
+	bool clk_en;
+
+	rate = clk_get_rate(priv->clk);
+	expect_period = min(div64_u64(ULLONG_MAX, (u64)rate), state->period);
+	dev_dbg(dev, "expect period: %lldns, duty_cycle: %lldns", expect_period,
+		state->duty_cycle);
+	/*
+	 * Pick the smallest value for div_h so that div_l can be the biggest
+	 * which results in a finer resolution near the target period value.
+	 */
+	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
+		  (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1);
+	div_h = order_base_2(DIV64_U64_ROUND_UP(rate * expect_period, divisor));
+	if (div_h > 0xf)
+		div_h = 0xf;
+
+	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) << div_h;
+	div_l = div64_u64(rate * expect_period, divisor);
+
+	if (div_l == 0)
+		return -ERANGE;
+
+	div_l -= 1;
+
+	if (div_l > 255)
+		div_l = 255;
+
+	dev_dbg(dev, "clk source: %ld div_h %lld, div_l : %lld\n", rate, div_h,
+		div_l);
+	/* duty_pt = duty_cycle * (PERIOD + 1) / period */
+	duty_pt = div64_u64(state->duty_cycle * rate,
+			    (u64)NSEC_PER_SEC * (div_l + 1) << div_h);
+	dev_dbg(dev, "duty_cycle = %lld, duty_pt = %d\n", state->duty_cycle,
+		duty_pt);
+
+	/*
+	 * Fixed DUTY_CYCLE_PERIOD to its max value to get a
+	 * fine-grained resolution for duty_cycle at the expense of a
+	 * coarser period resolution.
+	 */
+	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE(hwpwm),
+			   PWM_ASPEED_DUTY_CYCLE_PERIOD,
+			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
+				      PWM_ASPEED_FIXED_PERIOD));
+	if (duty_pt == 0) {
+		/* emit inactive level and assert the duty counter reset */
+		clk_en = 0;
+	} else {
+		clk_en = 1;
+		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
+			duty_pt = 0;
+		regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE(hwpwm),
+				   PWM_ASPEED_DUTY_CYCLE_RISING_POINT |
+					   PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
+				   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, duty_pt));
+	}
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL(hwpwm),
+			   PWM_ASPEED_CTRL_CLK_DIV_H | PWM_ASPEED_CTRL_CLK_DIV_L |
+				   PWM_ASPEED_CTRL_PIN_ENABLE | PWM_ASPEED_CTRL_CLK_ENABLE |
+				   PWM_ASPEED_CTRL_INVERSE,
+			   FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
+				   FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l) |
+				   FIELD_PREP(PWM_ASPEED_CTRL_PIN_ENABLE, state->enabled) |
+				   FIELD_PREP(PWM_ASPEED_CTRL_CLK_ENABLE, clk_en) |
+				   FIELD_PREP(PWM_ASPEED_CTRL_INVERSE, state->polarity));
+	return 0;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.apply = aspeed_pwm_apply,
+	.get_state = aspeed_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static void aspeed_pwm_reset_assert(void *data)
+{
+	struct reset_control *rst = data;
+
+	reset_control_assert(rst);
+}
+
+static void aspeed_pwm_chip_remove(void *data)
+{
+	struct pwm_chip *chip = data;
+
+	pwmchip_remove(chip);
+}
+
+static int aspeed_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+	struct aspeed_pwm_data *priv;
+	struct device_node *np;
+	struct platform_device *parent_dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	np = pdev->dev.parent->of_node;
+	if (!of_device_is_compatible(np, "aspeed,ast2600-pwm-tach"))
+		return dev_err_probe(dev, -ENODEV,
+				     "Unsupported pwm device binding\n");
+
+	priv->regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(priv->regmap))
+		return dev_err_probe(dev, PTR_ERR(priv->regmap),
+				     "Couldn't get regmap\n");
+
+	parent_dev = of_find_device_by_node(np);
+	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk),
+				     "Couldn't get clock\n");
+
+	priv->reset = devm_reset_control_get_shared(&parent_dev->dev, NULL);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "Couldn't get reset control\n");
+
+	ret = reset_control_deassert(priv->reset);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Couldn't deassert reset control\n");
+
+	ret = devm_add_action_or_reset(dev, aspeed_pwm_reset_assert,
+				       priv->reset);
+	if (ret)
+		return ret;
+
+	priv->chip.dev = dev;
+	priv->chip.ops = &aspeed_pwm_ops;
+	priv->chip.npwm = PWM_ASPEED_NR_PWMS;
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
+	ret = devm_add_action_or_reset(dev, aspeed_pwm_chip_remove,
+				       &priv->chip);
+	if (ret)
+		return ret;
+	return 0;
+}
+
+static const struct of_device_id of_pwm_match_table[] = {
+	{
+		.compatible = "aspeed,ast2600-pwm",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_pwm_match_table);
+
+static struct platform_driver aspeed_pwm_driver = {
+	.probe = aspeed_pwm_probe,
+	.driver	= {
+		.name = "aspeed-pwm",
+		.of_match_table = of_pwm_match_table,
+	},
+};
+
+module_platform_driver(aspeed_pwm_driver);
+
+MODULE_AUTHOR("Billy Tsai <[e-mail]>");
+MODULE_DESCRIPTION("Aspeed ast2600 PWM device driver");
+MODULE_LICENSE("GPL v2");