Re: [PATCH v14 5/8] coresight: tmc: Add support for reading crash data

On 12/02/2025 11:49, Linu Cherian wrote:

• 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

---

Changelog from v13:

• Changed the log levels of crc error check failure prints from dev_dbg to dev_err

• Added CRC recalculation upon barrier packet insertion for overflow cases, this fixes wrong crc check failures for subsequent boots

• Add metadata valid flag checks for successfully opening crashdata files

• Report to the user during probe if valid crash tracedata is found

• Few other trivial cleanups

  .../hwtracing/coresight/coresight-tmc-core.c | 226 +++++++++++++++++- .../hwtracing/coresight/coresight-tmc-etr.c | 22 +- drivers/hwtracing/coresight/coresight-tmc.h | 14 +- 3 files changed, 259 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c index c6224eed705d..045d37606750 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-core.c +++ b/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); }

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index fb944a68a11c..c92556e1b4db 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/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

diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h index d76e83fc840b..e3707b69abff 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/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 +318,8 @@ 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);

This is no longer required. I can fix this up at my end.

Suzuki

/* ETB/ETF functions */ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata); @@ -371,6 +382,7 @@ 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) {