diff mbox series

[v8,5/7] coresight: tmc: Add support for reading crash data

Message ID 20240531042745.494222-6-lcherian@marvell.com (mailing list archive)
State New, archived
Headers show
Series Coresight for Kernel panic and watchdog reset | expand

Commit Message

Linu Cherian May 31, 2024, 4:27 a.m. UTC
* Introduce a new mode CS_MODE_READ_CRASHDATA for reading trace
  captured in previous crash/watchdog reset.

* Add special device files for reading ETR/ETF crash data.

* User can read the crash data as below

  For example, for reading crash data from tmc_etf sink

  #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin

Signed-off-by: Anil Kumar Reddy <areddy3@marvell.com>
Signed-off-by: Tanmay Jagdale <tanmay@marvell.com>
Signed-off-by: Linu Cherian <lcherian@marvell.com>
---
Changelog from v7:
* Moved crash dev registration into new function,
  register_crash_dev_interface
* Removed redundant variable trace_addr in
  tmc_etr_setup_crashdata_buf

 .../coresight/coresight-etm4x-core.c          |   1 +
 .../hwtracing/coresight/coresight-tmc-core.c  | 148 ++++++++++++++++-
 .../hwtracing/coresight/coresight-tmc-etf.c   |  73 +++++++++
 .../hwtracing/coresight/coresight-tmc-etr.c   | 152 +++++++++++++++++-
 drivers/hwtracing/coresight/coresight-tmc.h   |  11 +-
 include/linux/coresight.h                     |  13 ++
 6 files changed, 391 insertions(+), 7 deletions(-)

Comments

James Clark May 31, 2024, 10:03 a.m. UTC | #1
On 31/05/2024 05:27, Linu Cherian wrote:
> * Introduce a new mode CS_MODE_READ_CRASHDATA for reading trace
>   captured in previous crash/watchdog reset.
> 
> * Add special device files for reading ETR/ETF crash data.
> 
> * User can read the crash data as below
> 
>   For example, for reading crash data from tmc_etf sink
> 
>   #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin
> 
> Signed-off-by: Anil Kumar Reddy <areddy3@marvell.com>
> Signed-off-by: Tanmay Jagdale <tanmay@marvell.com>
> Signed-off-by: Linu Cherian <lcherian@marvell.com>
> ---
> Changelog from v7:
> * Moved crash dev registration into new function,
>   register_crash_dev_interface
> * Removed redundant variable trace_addr in
>   tmc_etr_setup_crashdata_buf
> 
>  .../coresight/coresight-etm4x-core.c          |   1 +
>  .../hwtracing/coresight/coresight-tmc-core.c  | 148 ++++++++++++++++-
>  .../hwtracing/coresight/coresight-tmc-etf.c   |  73 +++++++++
>  .../hwtracing/coresight/coresight-tmc-etr.c   | 152 +++++++++++++++++-
>  drivers/hwtracing/coresight/coresight-tmc.h   |  11 +-
>  include/linux/coresight.h                     |  13 ++
>  6 files changed, 391 insertions(+), 7 deletions(-)
> 

[...]

> +static void register_crash_dev_interface(struct tmc_drvdata * drvdata,
> +					 const char *name)
> +{
> +	drvdata->crashdev.name =
> +		devm_kasprintf(&drvdata->csdev->dev, GFP_KERNEL, "%s_%s", "crash", name);
> +	drvdata->crashdev.minor = MISC_DYNAMIC_MINOR;
> +	drvdata->crashdev.fops = &tmc_crashdata_fops;
> +	if (misc_register(&drvdata->crashdev))
> +		dev_dbg(&drvdata->csdev->dev,
> +			"Failed to setup user interface for crashdata\n");
> +}
> +
>  static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  {
>  	int ret = 0;
> @@ -619,6 +752,10 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  		coresight_unregister(drvdata->csdev);
>  	else
>  		pm_runtime_put(&adev->dev);
> +
> +	if (is_tmc_reserved_region_valid(dev))
> +		register_crash_dev_interface(drvdata, desc.name);
> +

Now that you've added an extra step to the probe you need to add a "goto
out" when the previous step fails:

  if (ret) {
	coresight_unregister(drvdata->csdev);
+	goto out;
  }

That seems to be the pattern in the rest of the function. Otherwise you
might register the interface on no device.

There's also a conflict here and in some other places. Since this has to
go through the coresight branch you should base it off of coresight-next.

>  out:
>  	return ret;
>  }
> @@ -630,7 +767,8 @@ static void tmc_shutdown(struct amba_device *adev)
>  
>  	spin_lock_irqsave(&drvdata->spinlock, flags);
>  
> -	if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
> +	if ((coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED) ||
> +	    (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA))
>  		goto out;
>  
>  	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index f9569585e9f8..655c0c0ba54b 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -657,6 +657,56 @@ static int tmc_panic_sync_etf(struct coresight_device *csdev)
>  	return 0;
>  }
>  

[...]

> @@ -725,6 +789,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
>  		__tmc_etb_disable_hw(drvdata);
>  	}
>  
> +mode_valid:
>  	drvdata->reading = true;
>  out:
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> @@ -744,8 +809,16 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
>  			 drvdata->config_type != TMC_CONFIG_TYPE_ETF))
>  		return -EINVAL;
>  
> +

Whitespace change. There are a couple of other minor checkpatch style
warnings.

The rest looks good to me. All the tests are passing. I still think we
should all the kself test for this mode, but that can be done later.
Linu Cherian June 5, 2024, 4:46 a.m. UTC | #2
Hi James,

> -----Original Message-----
> From: James Clark <james.clark@arm.com>
> Sent: Friday, May 31, 2024 3:33 PM
> To: Linu Cherian <lcherian@marvell.com>
> Cc: linux-arm-kernel@lists.infradead.org; coresight@lists.linaro.org; linux-
> kernel@vger.kernel.org; robh+dt@kernel.org;
> krzysztof.kozlowski+dt@linaro.org; conor+dt@kernel.org;
> devicetree@vger.kernel.org; Sunil Kovvuri Goutham
> <sgoutham@marvell.com>; George Cherian <gcherian@marvell.com>; Anil
> Kumar Reddy H <areddy3@marvell.com>; Tanmay Jagdale
> <tanmay@marvell.com>; suzuki.poulose@arm.com; mike.leach@linaro.org
> Subject: [EXTERNAL] Re: [PATCH v8 5/7] coresight: tmc: Add support for
> reading crash data
> 
> Prioritize security for external emails: Confirm sender and content safety
> before clicking links or opening attachments
> 
> ----------------------------------------------------------------------
> 
> 
> On 31/05/2024 05:27, Linu Cherian wrote:
> > * Introduce a new mode CS_MODE_READ_CRASHDATA for reading trace
> >   captured in previous crash/watchdog reset.
> >
> > * Add special device files for reading ETR/ETF crash data.
> >
> > * User can read the crash data as below
> >
> >   For example, for reading crash data from tmc_etf sink
> >
> >   #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin
> >
> > Signed-off-by: Anil Kumar Reddy <areddy3@marvell.com>
> > Signed-off-by: Tanmay Jagdale <tanmay@marvell.com>
> > Signed-off-by: Linu Cherian <lcherian@marvell.com>
> > ---
> > Changelog from v7:
> > * Moved crash dev registration into new function,
> >   register_crash_dev_interface
> > * Removed redundant variable trace_addr in
> >   tmc_etr_setup_crashdata_buf
> >
> >  .../coresight/coresight-etm4x-core.c          |   1 +
> >  .../hwtracing/coresight/coresight-tmc-core.c  | 148 ++++++++++++++++-
> >  .../hwtracing/coresight/coresight-tmc-etf.c   |  73 +++++++++
> >  .../hwtracing/coresight/coresight-tmc-etr.c   | 152 +++++++++++++++++-
> >  drivers/hwtracing/coresight/coresight-tmc.h   |  11 +-
> >  include/linux/coresight.h                     |  13 ++
> >  6 files changed, 391 insertions(+), 7 deletions(-)
> >
> 
> [...]
> 
> > +static void register_crash_dev_interface(struct tmc_drvdata * drvdata,
> > +					 const char *name)
> > +{
> > +	drvdata->crashdev.name =
> > +		devm_kasprintf(&drvdata->csdev->dev, GFP_KERNEL,
> "%s_%s", "crash", name);
> > +	drvdata->crashdev.minor = MISC_DYNAMIC_MINOR;
> > +	drvdata->crashdev.fops = &tmc_crashdata_fops;
> > +	if (misc_register(&drvdata->crashdev))
> > +		dev_dbg(&drvdata->csdev->dev,
> > +			"Failed to setup user interface for crashdata\n"); }
> > +
> >  static int tmc_probe(struct amba_device *adev, const struct amba_id
> > *id)  {
> >  	int ret = 0;
> > @@ -619,6 +752,10 @@ static int tmc_probe(struct amba_device *adev,
> const struct amba_id *id)
> >  		coresight_unregister(drvdata->csdev);
> >  	else
> >  		pm_runtime_put(&adev->dev);
> > +
> > +	if (is_tmc_reserved_region_valid(dev))
> > +		register_crash_dev_interface(drvdata, desc.name);
> > +
> 
> Now that you've added an extra step to the probe you need to add a "goto
> out" when the previous step fails:
> 
>   if (ret) {
> 	coresight_unregister(drvdata->csdev);
> +	goto out;
>   }
> 
> That seems to be the pattern in the rest of the function. Otherwise you
> might register the interface on no device.
> 
> There's also a conflict here and in some other places. Since this has to go
> through the coresight branch you should base it off of coresight-next.
> 


Ack.

> >  out:
> >  	return ret;
> >  }
> > @@ -630,7 +767,8 @@ static void tmc_shutdown(struct amba_device
> *adev)
> >
> >  	spin_lock_irqsave(&drvdata->spinlock, flags);
> >
> > -	if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
> > +	if ((coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
> ||
> > +	    (coresight_get_mode(drvdata->csdev) ==
> CS_MODE_READ_CRASHDATA))
> >  		goto out;
> >
> >  	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) diff --git
> > a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > index f9569585e9f8..655c0c0ba54b 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > @@ -657,6 +657,56 @@ static int tmc_panic_sync_etf(struct
> coresight_device *csdev)
> >  	return 0;
> >  }
> >
> 
> [...]
> 
> > @@ -725,6 +789,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata
> *drvdata)
> >  		__tmc_etb_disable_hw(drvdata);
> >  	}
> >
> > +mode_valid:
> >  	drvdata->reading = true;
> >  out:
> >  	spin_unlock_irqrestore(&drvdata->spinlock, flags); @@ -744,8
> +809,16
> > @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
> >  			 drvdata->config_type != TMC_CONFIG_TYPE_ETF))
> >  		return -EINVAL;
> >
> > +
> 
> Whitespace change. There are a couple of other minor checkpatch style
> warnings.


Ack.

> 
> The rest looks good to me. All the tests are passing. I still think we should all
> the kself test for this mode, but that can be done later.


Sure. Will add kself tests for sysfs mode and send it as separate patches.
diff mbox series

Patch

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index c2ca4a02dfce..5eb411e39b01 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1011,6 +1011,7 @@  static void etm4_disable(struct coresight_device *csdev,
 
 	switch (mode) {
 	case CS_MODE_DISABLED:
+	case CS_MODE_READ_CRASHDATA:
 		break;
 	case CS_MODE_SYSFS:
 		etm4_disable_sysfs(csdev);
diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index 7170416c3e1a..aaa9de9f4cd2 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -103,6 +103,60 @@  u32 tmc_get_memwidth_mask(struct tmc_drvdata *drvdata)
 	return mask;
 }
 
+int tmc_read_prepare_crashdata(struct tmc_drvdata *drvdata)
+{
+	int ret = 0;
+	struct tmc_crash_metadata *mdata;
+	struct coresight_device *csdev = drvdata->csdev;
+
+	if (!drvdata->crash_mdata.vaddr) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mdata = drvdata->crash_mdata.vaddr;
+	/* Check data integrity of metadata */
+	if (mdata->crc32_mdata != find_crash_metadata_crc(mdata)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"CRC mismatch in tmc crash metadata\n");
+		ret = -EINVAL;
+		goto out;
+	}
+	/* Check data integrity of tracedata */
+	if (mdata->crc32_tdata != find_crash_tracedata_crc(drvdata, mdata)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"CRC mismatch in tmc crash tracedata\n");
+		ret = -EINVAL;
+		goto out;
+	}
+	/* Check for valid metadata */
+	if (!mdata->valid) {
+		dev_dbg(&drvdata->csdev->dev,
+			"Data invalid in tmc crash metadata\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Sink specific crashdata mode preparation */
+	ret = crashdata_ops(csdev)->prepare(csdev);
+	if (ret)
+		goto out;
+
+	if (mdata->sts & 0x1)
+		coresight_insert_barrier_packet(drvdata->buf);
+
+out:
+	return ret;
+}
+
+int tmc_read_unprepare_crashdata(struct tmc_drvdata *drvdata)
+{
+	struct coresight_device *csdev = drvdata->csdev;
+
+	/* Sink specific crashdata mode preparation */
+	return crashdata_ops(csdev)->unprepare(csdev);
+}
+
 static int tmc_read_prepare(struct tmc_drvdata *drvdata)
 {
 	int ret = 0;
@@ -153,6 +207,9 @@  static int tmc_open(struct inode *inode, struct file *file)
 	struct tmc_drvdata *drvdata = container_of(file->private_data,
 						   struct tmc_drvdata, miscdev);
 
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA)
+		return -EBUSY;
+
 	ret = tmc_read_prepare(drvdata);
 	if (ret)
 		return ret;
@@ -177,13 +234,12 @@  static inline ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata,
 	return -EINVAL;
 }
 
-static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
-			loff_t *ppos)
+static ssize_t tmc_read_common(struct tmc_drvdata *drvdata, char __user *data,
+			       size_t len, loff_t *ppos)
 {
 	char *bufp;
 	ssize_t actual;
-	struct tmc_drvdata *drvdata = container_of(file->private_data,
-						   struct tmc_drvdata, miscdev);
+
 	actual = tmc_get_sysfs_trace(drvdata, *ppos, len, &bufp);
 	if (actual <= 0)
 		return 0;
@@ -200,6 +256,16 @@  static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
 	return actual;
 }
 
+static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
+			loff_t *ppos)
+{
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata, miscdev);
+
+	return tmc_read_common(drvdata, data, len, ppos);
+}
+
+
 static int tmc_release(struct inode *inode, struct file *file)
 {
 	int ret;
@@ -222,6 +288,61 @@  static const struct file_operations tmc_fops = {
 	.llseek		= no_llseek,
 };
 
+static int tmc_crashdata_open(struct inode *inode, struct file *file)
+{
+	int ret;
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata,
+						   crashdev);
+
+	if (!coresight_take_mode(drvdata->csdev, CS_MODE_READ_CRASHDATA))
+		return -EBUSY;
+
+	ret = tmc_read_prepare(drvdata);
+	if (ret) {
+		coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
+		return ret;
+	}
+
+	nonseekable_open(inode, file);
+
+	dev_dbg(&drvdata->csdev->dev, "%s: successfully opened\n", __func__);
+	return 0;
+}
+
+static ssize_t tmc_crashdata_read(struct file *file, char __user *data,
+				  size_t len, loff_t *ppos)
+{
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata,
+						   crashdev);
+
+	return tmc_read_common(drvdata, data, len, ppos);
+}
+
+static int tmc_crashdata_release(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata,
+						   crashdev);
+
+	ret = tmc_read_unprepare(drvdata);
+
+	coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
+
+	dev_dbg(&drvdata->csdev->dev, "%s: released\n", __func__);
+	return ret;
+}
+
+static const struct file_operations tmc_crashdata_fops = {
+	.owner		= THIS_MODULE,
+	.open		= tmc_crashdata_open,
+	.read		= tmc_crashdata_read,
+	.release	= tmc_crashdata_release,
+	.llseek		= no_llseek,
+};
+
 static enum tmc_mem_intf_width tmc_get_memwidth(u32 devid)
 {
 	enum tmc_mem_intf_width memwidth;
@@ -507,6 +628,18 @@  static u32 tmc_etr_get_max_burst_size(struct device *dev)
 	return burst_size;
 }
 
+static void register_crash_dev_interface(struct tmc_drvdata * drvdata,
+					 const char *name)
+{
+	drvdata->crashdev.name =
+		devm_kasprintf(&drvdata->csdev->dev, GFP_KERNEL, "%s_%s", "crash", name);
+	drvdata->crashdev.minor = MISC_DYNAMIC_MINOR;
+	drvdata->crashdev.fops = &tmc_crashdata_fops;
+	if (misc_register(&drvdata->crashdev))
+		dev_dbg(&drvdata->csdev->dev,
+			"Failed to setup user interface for crashdata\n");
+}
+
 static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 {
 	int ret = 0;
@@ -619,6 +752,10 @@  static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 		coresight_unregister(drvdata->csdev);
 	else
 		pm_runtime_put(&adev->dev);
+
+	if (is_tmc_reserved_region_valid(dev))
+		register_crash_dev_interface(drvdata, desc.name);
+
 out:
 	return ret;
 }
@@ -630,7 +767,8 @@  static void tmc_shutdown(struct amba_device *adev)
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
-	if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
+	if ((coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED) ||
+	    (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA))
 		goto out;
 
 	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index f9569585e9f8..655c0c0ba54b 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -657,6 +657,56 @@  static int tmc_panic_sync_etf(struct coresight_device *csdev)
 	return 0;
 }
 
+static int tmc_etb_setup_crashdata_buf(struct tmc_drvdata *drvdata)
+{
+	unsigned long size;
+	struct tmc_crash_metadata *mdata;
+	struct device *dev = &drvdata->csdev->dev;
+
+	mdata = drvdata->crash_mdata.vaddr;
+	size = mdata->size << 2;
+
+	/*
+	 * Buffer address given by metadata for retrieval of trace data
+	 * from previous boot is expected to be same as the reserved
+	 * trace buffer memory region provided through DTS
+	 */
+	if (is_tmc_reserved_region_valid(dev->parent)
+	    && (drvdata->crash_tbuf.paddr == mdata->trc_paddr))
+		drvdata->buf = drvdata->crash_tbuf.vaddr;
+	else {
+		dev_dbg(dev, "Trace buffer address of previous boot invalid\n");
+		return -EINVAL;
+	}
+
+	drvdata->len = size;
+	return 0;
+}
+
+static void tmc_etb_free_crashdata_buf(struct tmc_drvdata *drvdata)
+{
+	void *buf = drvdata->buf;
+
+	if (!buf)
+		return;
+	drvdata->buf = NULL;
+}
+
+static int tmc_etb_prepare_crashdata(struct coresight_device *csdev)
+{
+	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	return  tmc_etb_setup_crashdata_buf(drvdata);
+}
+
+static int tmc_etb_unprepare_crashdata(struct coresight_device *csdev)
+{
+	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	tmc_etb_free_crashdata_buf(drvdata);
+	return 0;
+}
+
 static const struct coresight_ops_sink tmc_etf_sink_ops = {
 	.enable		= tmc_enable_etf_sink,
 	.disable	= tmc_disable_etf_sink,
@@ -674,6 +724,11 @@  static const struct coresight_ops_panic tmc_etf_sync_ops = {
 	.sync		= tmc_panic_sync_etf,
 };
 
+static const struct coresight_ops_crashdata tmc_etf_crashdata_ops = {
+	.prepare	= tmc_etb_prepare_crashdata,
+	.unprepare	= tmc_etb_unprepare_crashdata,
+};
+
 const struct coresight_ops tmc_etb_cs_ops = {
 	.sink_ops	= &tmc_etf_sink_ops,
 };
@@ -682,6 +737,7 @@  const struct coresight_ops tmc_etf_cs_ops = {
 	.sink_ops	= &tmc_etf_sink_ops,
 	.link_ops	= &tmc_etf_link_ops,
 	.panic_ops	= &tmc_etf_sync_ops,
+	.crashdata_ops	= &tmc_etf_crashdata_ops,
 };
 
 int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
@@ -702,6 +758,14 @@  int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 		goto out;
 	}
 
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA) {
+		ret = tmc_read_prepare_crashdata(drvdata);
+		if (ret)
+			goto out;
+		else
+			goto mode_valid;
+	}
+
 	/* Don't interfere if operated from Perf */
 	if (coresight_get_mode(drvdata->csdev) == CS_MODE_PERF) {
 		ret = -EINVAL;
@@ -725,6 +789,7 @@  int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 		__tmc_etb_disable_hw(drvdata);
 	}
 
+mode_valid:
 	drvdata->reading = true;
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -744,8 +809,16 @@  int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
 			 drvdata->config_type != TMC_CONFIG_TYPE_ETF))
 		return -EINVAL;
 
+
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA) {
+		tmc_read_unprepare_crashdata(drvdata);
+		drvdata->reading = false;
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return 0;
+	}
+
 	/* Re-enable the TMC if need be */
 	if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS) {
 		/* There is no point in reading a TMC in HW FIFO mode */
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index be1079e8fd64..74f53972ce3c 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1160,7 +1160,12 @@  ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata,
 {
 	s64 offset;
 	ssize_t actual = len;
-	struct etr_buf *etr_buf = drvdata->sysfs_buf;
+	struct etr_buf *etr_buf;
+
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA)
+		etr_buf = drvdata->sysfs_crash_buf;
+	else
+		etr_buf = drvdata->sysfs_buf;
 
 	if (pos + actual > etr_buf->len)
 		actual = etr_buf->len - pos;
@@ -1878,6 +1883,128 @@  static int tmc_panic_sync_etr(struct coresight_device *csdev)
 	return 0;
 }
 
+static int tmc_etr_setup_crashdata_buf(struct tmc_drvdata *drvdata)
+{
+	int rc = 0;
+	struct etr_buf *etr_buf;
+	struct etr_flat_buf *resrv_buf;
+	struct tmc_crash_metadata *mdata;
+	struct device *dev = &drvdata->csdev->dev;
+
+	mdata = drvdata->crash_mdata.vaddr;
+
+	etr_buf = kzalloc(sizeof(*etr_buf), GFP_ATOMIC);
+	if (!etr_buf) {
+		rc = -ENOMEM;
+		goto out;
+	}
+	etr_buf->size = drvdata->crash_tbuf.size;
+
+	resrv_buf = kzalloc(sizeof(*resrv_buf), GFP_ATOMIC);
+	if (!resrv_buf) {
+		rc = -ENOMEM;
+		goto rmem_err;
+	}
+
+	/*
+	 * Buffer address given by metadata for retrieval of trace data
+	 * from previous boot is expected to be same as the reserved
+	 * trace buffer memory region provided through DTS
+	 */
+	if (is_tmc_reserved_region_valid(dev->parent)
+	    && (drvdata->crash_tbuf.paddr == mdata->trc_paddr))
+		resrv_buf->vaddr = drvdata->crash_tbuf.vaddr;
+	else {
+		dev_dbg(dev, "Trace buffer address of previous boot invalid\n");
+		rc = -EINVAL;
+		goto map_err;
+	}
+
+	resrv_buf->size = etr_buf->size;
+	resrv_buf->dev = &drvdata->csdev->dev;
+	etr_buf->mode = ETR_MODE_RESRV;
+	etr_buf->private = resrv_buf;
+	etr_buf->ops = etr_buf_ops[ETR_MODE_RESRV];
+
+	drvdata->sysfs_crash_buf = etr_buf;
+
+	return 0;
+
+map_err:
+	kfree(resrv_buf);
+
+rmem_err:
+	kfree(etr_buf);
+
+out:
+	return rc;
+}
+
+static int tmc_etr_sync_crashdata_buf(struct tmc_drvdata *drvdata)
+{
+	u32 status;
+	u64 rrp, rwp, dba;
+	struct tmc_crash_metadata *mdata;
+	struct etr_buf *etr_buf = drvdata->sysfs_crash_buf;
+
+	mdata = drvdata->crash_mdata.vaddr;
+
+	rrp = mdata->rrp;
+	rwp = mdata->rwp;
+	dba = mdata->dba;
+	status = mdata->sts;
+
+	etr_buf->full = !!(status & TMC_STS_FULL);
+
+	/* Sync the buffer pointers */
+	etr_buf->offset = rrp - dba;
+	if (etr_buf->full)
+		etr_buf->len = etr_buf->size;
+	else
+		etr_buf->len = rwp - rrp;
+
+	/* Additional sanity checks for validating metadata */
+	if ((etr_buf->offset > etr_buf->size) ||
+	    (etr_buf->len > etr_buf->size)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"Offset and length invalid in tmc crash metadata\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void tmc_etr_free_crashdata_buf(struct tmc_drvdata *drvdata)
+{
+	struct etr_buf *etr_buf = drvdata->sysfs_crash_buf;
+
+	if (!etr_buf)
+		return;
+	drvdata->sysfs_crash_buf = NULL;
+}
+
+static int tmc_etr_prepare_crashdata(struct coresight_device *csdev)
+{
+	int ret = 0;
+	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	ret = tmc_etr_setup_crashdata_buf(drvdata);
+	if (ret)
+		goto out;
+	ret = tmc_etr_sync_crashdata_buf(drvdata);
+
+out:
+	return ret;
+}
+
+static int tmc_etr_unprepare_crashdata(struct coresight_device *csdev)
+{
+	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	tmc_etr_free_crashdata_buf(drvdata);
+	return 0;
+}
+
 static const struct coresight_ops_sink tmc_etr_sink_ops = {
 	.enable		= tmc_enable_etr_sink,
 	.disable	= tmc_disable_etr_sink,
@@ -1890,9 +2017,15 @@  static const struct coresight_ops_panic tmc_etr_sync_ops = {
 	.sync		= tmc_panic_sync_etr,
 };
 
+static const struct coresight_ops_crashdata tmc_etr_crashdata_ops = {
+	.prepare	= tmc_etr_prepare_crashdata,
+	.unprepare	= tmc_etr_unprepare_crashdata,
+};
+
 const struct coresight_ops tmc_etr_cs_ops = {
 	.sink_ops	= &tmc_etr_sink_ops,
 	.panic_ops	= &tmc_etr_sync_ops,
+	.crashdata_ops	= &tmc_etr_crashdata_ops,
 };
 
 int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
@@ -1904,12 +2037,21 @@  int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 	if (WARN_ON_ONCE(drvdata->config_type != TMC_CONFIG_TYPE_ETR))
 		return -EINVAL;
 
+
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 	if (drvdata->reading) {
 		ret = -EBUSY;
 		goto out;
 	}
 
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA) {
+		ret = tmc_read_prepare_crashdata(drvdata);
+		if (ret)
+			goto out;
+		else
+			goto mode_valid;
+	}
+
 	/*
 	 * We can safely allow reads even if the ETR is operating in PERF mode,
 	 * since the sysfs session is captured in mode specific data.
@@ -1924,6 +2066,7 @@  int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 	if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
 		__tmc_etr_disable_hw(drvdata);
 
+mode_valid:
 	drvdata->reading = true;
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -1942,6 +2085,12 @@  int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA) {
+		sysfs_buf = drvdata->sysfs_crash_buf;
+		tmc_read_unprepare_crashdata(drvdata);
+		goto out;
+	}
+
 	/* RE-enable the TMC if need be */
 	if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS) {
 		/*
@@ -1959,6 +2108,7 @@  int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)
 		drvdata->sysfs_buf = NULL;
 	}
 
+out:
 	drvdata->reading = false;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 875d4129da7c..528174283ecc 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -200,6 +200,8 @@  struct tmc_resrv_buf {
  * @base:	memory mapped base address for this component.
  * @csdev:	component vitals needed by the framework.
  * @miscdev:	specifics to handle "/dev/xyz.tmc" entry.
+ * @crashdev:	specifics to handle "/dev/crash_tmc_xyz" entry for reading
+ *		crash tracedata.
  * @spinlock:	only one at a time pls.
  * @pid:	Process ID of the process being monitored by the session
  *		that is using this component.
@@ -218,7 +220,10 @@  struct tmc_resrv_buf {
  * @idr_mutex:	Access serialisation for idr.
  * @sysfs_buf:	SYSFS buffer for ETR.
  * @perf_buf:	PERF buffer for ETR.
- * @crash_tbuf:	Used by ETR as hardware trace buffer and for trace data
+ * @sysfs_crash_buf: Sysfs crashdata buffer for ETR. This is a special purpose
+ *		buffer that is used only for mapping the trace buffer from
+ *		previous crash and not for capturing trace.
+ * @crash_tbuf: Used by ETR as hardware trace buffer and for trace data
  *		retention (after crash) only when ETR_MODE_RESRV buffer
  *		mode is enabled. Used by ETF for trace data retention
  *		(after crash) by default.
@@ -229,6 +234,7 @@  struct tmc_drvdata {
 	void __iomem		*base;
 	struct coresight_device	*csdev;
 	struct miscdevice	miscdev;
+	struct miscdevice	crashdev;
 	spinlock_t		spinlock;
 	pid_t			pid;
 	bool			reading;
@@ -248,6 +254,7 @@  struct tmc_drvdata {
 	struct mutex		idr_mutex;
 	struct etr_buf		*sysfs_buf;
 	struct etr_buf		*perf_buf;
+	struct etr_buf		*sysfs_crash_buf;
 	struct tmc_resrv_buf	crash_tbuf;
 	struct tmc_resrv_buf	crash_mdata;
 };
@@ -299,6 +306,8 @@  void tmc_flush_and_stop(struct tmc_drvdata *drvdata);
 void tmc_enable_hw(struct tmc_drvdata *drvdata);
 void tmc_disable_hw(struct tmc_drvdata *drvdata);
 u32 tmc_get_memwidth_mask(struct tmc_drvdata *drvdata);
+int tmc_read_prepare_crashdata(struct tmc_drvdata *drvdata);
+int tmc_read_unprepare_crashdata(struct tmc_drvdata *drvdata);
 
 /* ETB/ETF functions */
 int tmc_read_prepare_etb(struct tmc_drvdata *drvdata);
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index b156467c9baa..b5e825b25e9d 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -308,6 +308,7 @@  enum cs_mode {
 	CS_MODE_DISABLED,
 	CS_MODE_SYSFS,
 	CS_MODE_PERF,
+	CS_MODE_READ_CRASHDATA, /* Trace data from previous crash */
 };
 
 #define source_ops(csdev)	csdev->ops->source_ops
@@ -316,6 +317,7 @@  enum cs_mode {
 #define helper_ops(csdev)	csdev->ops->helper_ops
 #define ect_ops(csdev)		csdev->ops->ect_ops
 #define panic_ops(csdev)	csdev->ops->panic_ops
+#define crashdata_ops(csdev)	csdev->ops->crashdata_ops
 
 /**
  * struct coresight_ops_sink - basic operations for a sink
@@ -395,12 +397,23 @@  struct coresight_ops_panic {
 	int (*sync)(struct coresight_device *csdev);
 };
 
+/**
+ * struct coresight_ops_crashdata - Generic device ops for crashdata mode
+ *
+ * @prepare	: Preparation for reading crashdata mode
+ */
+struct coresight_ops_crashdata {
+	int (*prepare)(struct coresight_device *csdev);
+	int (*unprepare)(struct coresight_device *csdev);
+};
+
 struct coresight_ops {
 	const struct coresight_ops_sink *sink_ops;
 	const struct coresight_ops_link *link_ops;
 	const struct coresight_ops_source *source_ops;
 	const struct coresight_ops_helper *helper_ops;
 	const struct coresight_ops_panic *panic_ops;
+	const struct coresight_ops_crashdata *crashdata_ops;
 };
 
 static inline u32 csdev_access_relaxed_read32(struct csdev_access *csa,