coresight: tmc: Add support for reading crash data

* Add support for reading crashdata using special device files.
  The special device files /dev/crash_tmc_xxx would be available
  for read file operation only when the crash data is valid.

* 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>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250212114918.548431-6-lcherian@marvell.com

drivers/hwtracing/coresight/coresight-tmc-core.c

@@ -105,6 +105,128 @@ u32 tmc_get_memwidth_mask(struct tmc_drvdata *drvdata)
 	return mask;
 }
 
+static bool is_tmc_crashdata_valid(struct tmc_drvdata *drvdata)
+{
+	struct tmc_crash_metadata *mdata;
+
+	if (!tmc_has_reserved_buffer(drvdata) ||
+	    !tmc_has_crash_mdata_buffer(drvdata))
+		return false;
+
+	mdata = drvdata->crash_mdata.vaddr;
+
+	/* Check version match */
+	if (mdata->version != CS_CRASHDATA_VERSION)
+		return false;
+
+	/* Check for valid metadata */
+	if (!mdata->valid) {
+		dev_dbg(&drvdata->csdev->dev,
+			"Data invalid in tmc crash metadata\n");
+		return false;
+	}
+
+	/*
+	 * 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 (drvdata->resrv_buf.paddr != mdata->trace_paddr) {
+		dev_dbg(&drvdata->csdev->dev,
+			"Trace buffer address of previous boot invalid\n");
+		return false;
+	}
+
+	/* Check data integrity of metadata */
+	if (mdata->crc32_mdata != find_crash_metadata_crc(mdata)) {
+		dev_err(&drvdata->csdev->dev,
+			"CRC mismatch in tmc crash metadata\n");
+		return false;
+	}
+	/* Check data integrity of tracedata */
+	if (mdata->crc32_tdata != find_crash_tracedata_crc(drvdata, mdata)) {
+		dev_err(&drvdata->csdev->dev,
+			"CRC mismatch in tmc crash tracedata\n");
+		return false;
+	}
+
+	return true;
+}
+
+static inline ssize_t tmc_get_resvbuf_trace(struct tmc_drvdata *drvdata,
+					  loff_t pos, size_t len, char **bufpp)
+{
+	s64 offset;
+	ssize_t actual = len;
+	struct tmc_resrv_buf *rbuf = &drvdata->resrv_buf;
+
+	if (pos + actual > rbuf->len)
+		actual = rbuf->len - pos;
+	if (actual <= 0)
+		return 0;
+
+	/* Compute the offset from which we read the data */
+	offset = rbuf->offset + pos;
+	if (offset >= rbuf->size)
+		offset -= rbuf->size;
+
+	/* Adjust the length to limit this transaction to end of buffer */
+	actual = (actual < (rbuf->size - offset)) ?
+		actual : rbuf->size - offset;
+
+	*bufpp = (char *)rbuf->vaddr + offset;
+
+	return actual;
+}
+
+static int tmc_prepare_crashdata(struct tmc_drvdata *drvdata)
+{
+	char *bufp;
+	ssize_t len;
+	u32 status, size;
+	u64 rrp, rwp, dba;
+	struct tmc_resrv_buf *rbuf;
+	struct tmc_crash_metadata *mdata;
+
+	mdata = drvdata->crash_mdata.vaddr;
+	rbuf = &drvdata->resrv_buf;
+
+	rrp = mdata->tmc_rrp;
+	rwp = mdata->tmc_rwp;
+	dba = mdata->tmc_dba;
+	status = mdata->tmc_sts;
+	size = mdata->tmc_ram_size << 2;
+
+	/* Sync the buffer pointers */
+	rbuf->offset = rrp - dba;
+	if (status & TMC_STS_FULL)
+		rbuf->len = size;
+	else
+		rbuf->len = rwp - rrp;
+
+	/* Additional sanity checks for validating metadata */
+	if ((rbuf->offset > size) ||
+	    (rbuf->len > size)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"Offset and length invalid in tmc crash metadata\n");
+		return -EINVAL;
+	}
+
+	if (status & TMC_STS_FULL) {
+		len = tmc_get_resvbuf_trace(drvdata, 0x0,
+					    CORESIGHT_BARRIER_PKT_SIZE, &bufp);
+		if (len >= CORESIGHT_BARRIER_PKT_SIZE) {
+			coresight_insert_barrier_packet(bufp);
+			/* Recalculate crc */
+			mdata->crc32_tdata = find_crash_tracedata_crc(drvdata,
+								      mdata);
+			mdata->crc32_mdata = find_crash_metadata_crc(mdata);
+		}
+	}
+
+	return 0;
+}
+
 static int tmc_read_prepare(struct tmc_drvdata *drvdata)
 {
 	int ret = 0;
@@ -223,6 +345,84 @@ static const struct file_operations tmc_fops = {
 	.release	= tmc_release,
 };
 
+static int tmc_crashdata_open(struct inode *inode, struct file *file)
+{
+	int err = 0;
+	unsigned long flags;
+	struct tmc_resrv_buf *rbuf;
+	struct tmc_crash_metadata *mdata;
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata,
+						   crashdev);
+
+	mdata = drvdata->crash_mdata.vaddr;
+	rbuf = &drvdata->resrv_buf;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	if (mdata->valid)
+		rbuf->reading = true;
+	else
+		err = -ENOENT;
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	if (err)
+		goto exit;
+
+	nonseekable_open(inode, file);
+	dev_dbg(&drvdata->csdev->dev, "%s: successfully opened\n", __func__);
+exit:
+	return err;
+}
+
+static ssize_t tmc_crashdata_read(struct file *file, 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,
+						   crashdev);
+
+	actual = tmc_get_resvbuf_trace(drvdata, *ppos, len, &bufp);
+	if (actual <= 0)
+		return 0;
+
+	if (copy_to_user(data, bufp, actual)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"%s: copy_to_user failed\n", __func__);
+		return -EFAULT;
+	}
+
+	*ppos += actual;
+	dev_dbg(&drvdata->csdev->dev, "%zu bytes copied\n", actual);
+
+	return actual;
+}
+
+static int tmc_crashdata_release(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+	unsigned long flags;
+	struct tmc_resrv_buf *rbuf;
+	struct tmc_drvdata *drvdata = container_of(file->private_data,
+						   struct tmc_drvdata,
+						   crashdev);
+
+	rbuf = &drvdata->resrv_buf;
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	rbuf->reading = false;
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+
+	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,
+};
+
 static enum tmc_mem_intf_width tmc_get_memwidth(u32 devid)
 {
 	enum tmc_mem_intf_width memwidth;
@@ -532,6 +732,22 @@ 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");
+		drvdata->crashdev.fops = NULL;
+	} else
+		dev_info(&drvdata->csdev->dev,
+			"Valid crash tracedata found\n");
+}
+
 static int __tmc_probe(struct device *dev, struct resource *res)
 {
 	int ret = 0;
@@ -632,9 +848,15 @@ static int __tmc_probe(struct device *dev, struct resource *res)
 	drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;
 	drvdata->miscdev.fops = &tmc_fops;
 	ret = misc_register(&drvdata->miscdev);
-	if (ret)
+	if (ret) {
 		coresight_unregister(drvdata->csdev);
+		goto out;
+	}
+
 out:
+	if (is_tmc_crashdata_valid(drvdata) &&
+	    !tmc_prepare_crashdata(drvdata))
+		register_crash_dev_interface(drvdata, desc.name);
 	return ret;
 }
 
@@ -687,6 +909,8 @@ static void __tmc_remove(struct device *dev)
 	 * handler to this device is closed.
 	 */
 	misc_deregister(&drvdata->miscdev);
+	if (drvdata->crashdev.fops)
+		misc_deregister(&drvdata->crashdev);
 	coresight_unregister(drvdata->csdev);
 }
 

drivers/hwtracing/coresight/coresight-tmc-etr.c

@@ -2012,6 +2012,26 @@ static ssize_t buf_mode_preferred_show(struct device *dev,
 	return sysfs_emit(buf, "%s\n", buf_modes_str[drvdata->etr_mode]);
 }
 
+static int buf_mode_set_resrv(struct tmc_drvdata *drvdata)
+{
+	int err = -EBUSY;
+	unsigned long flags;
+	struct tmc_resrv_buf *rbuf;
+
+	rbuf = &drvdata->resrv_buf;
+
+	/* Ensure there are no active crashdata read sessions */
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	if (!rbuf->reading) {
+		tmc_crashdata_set_invalid(drvdata);
+		rbuf->len = 0;
+		drvdata->etr_mode = ETR_MODE_RESRV;
+		err = 0;
+	}
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	return err;
+}
+
 static ssize_t buf_mode_preferred_store(struct device *dev,
 					  struct device_attribute *attr,
 					  const char *buf, size_t size)
@@ -2027,7 +2047,7 @@ static ssize_t buf_mode_preferred_store(struct device *dev,
 	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_CATU]) && buf_hw.has_catu)
 		drvdata->etr_mode = ETR_MODE_CATU;
 	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_RESRV]) && buf_hw.has_resrv)
-		drvdata->etr_mode = ETR_MODE_RESRV;
+		return buf_mode_set_resrv(drvdata) ? : size;
 	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_AUTO]))
 		drvdata->etr_mode = ETR_MODE_AUTO;
 	else

drivers/hwtracing/coresight/coresight-tmc.h

@@ -195,11 +195,17 @@ struct etr_buf {
  * @paddr	: Start address of reserved memory region.
  * @vaddr	: Corresponding CPU virtual address.
  * @size	: Size of reserved memory region.
+ * @offset	: Offset of the trace data in the buffer for consumption.
+ * @reading	: Flag to indicate if reading is active
+ * @len	: Available trace data @buf (may round up to the beginning).
  */
 struct tmc_resrv_buf {
 	phys_addr_t     paddr;
 	void		*vaddr;
 	size_t		size;
+	unsigned long	offset;
+	bool		reading;
+	s64		len;
 };
 
 /**
@@ -208,6 +214,8 @@ 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 that owns the session that is using
  *		this component. For example this would be the pid of the Perf
@@ -227,7 +235,7 @@ struct tmc_resrv_buf {
  * @idr_mutex:	Access serialisation for idr.
  * @sysfs_buf:	SYSFS buffer for ETR.
  * @perf_buf:	PERF buffer for ETR.
- * @resrv_buf:	Used by ETR as hardware trace buffer and for trace data
+ * @resrv_buf:  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.
@@ -239,6 +247,7 @@ struct tmc_drvdata {
 	void __iomem		*base;
 	struct coresight_device	*csdev;
 	struct miscdevice	miscdev;
+	struct miscdevice	crashdev;
 	spinlock_t		spinlock;
 	pid_t			pid;
 	bool			reading;
@@ -309,6 +318,7 @@ 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);
 
 /* ETB/ETF functions */
 int tmc_read_prepare_etb(struct tmc_drvdata *drvdata);
@@ -371,6 +381,7 @@ void tmc_sg_table_sync_data_range(struct tmc_sg_table *table,
 				  u64 offset, u64 size);
 ssize_t tmc_sg_table_get_data(struct tmc_sg_table *sg_table,
 			      u64 offset, size_t len, char **bufpp);
+
 static inline unsigned long
 tmc_sg_table_buf_size(struct tmc_sg_table *sg_table)
 {