[PATCH v3] coresight: tpdm: add traceid_show for checking traceid

Jie Gan
2026-03-25T03:10:38Z

Save the trace ID in drvdata during TPDM enablement and expose it
to userspace to support trace data parsing.

The TPDM device’s trace ID corresponds to the trace ID allocated
to the connected TPDA device.

Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
---
Changes in v3:
1. Only allow user to read the traceid while the TPDM device is enabled.
- Link to v2: https://lore.kernel.org/r/20260316-add-traceid-show-for-tpdm-v2-1-1dec2a67e4ed@oss.qualcomm.com

Changes in V2:
1. Use sysfs_emit instead of sprintf.
Link to V1 - https://lore.kernel.org/all/20260306-add-traceid-show-for-tpdm-v1-1-0658a8edb972@oss.qualcomm.com/
---
drivers/hwtracing/coresight/coresight-tpdm.c | 34 +++++++++++++++++++++++++++-
drivers/hwtracing/coresight/coresight-tpdm.h | 2 ++
2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
index da77bdaad0a4..c8339b973bfc 100644
--- a/drivers/hwtracing/coresight/coresight-tpdm.c
+++ b/drivers/hwtracing/coresight/coresight-tpdm.c
@@ -481,7 +481,7 @@ static void __tpdm_enable(struct tpdm_drvdata *drvdata)

static int tpdm_enable(struct coresight_device *csdev, struct perf_event *event,
enum cs_mode mode,
- __maybe_unused struct coresight_path *path)
+ struct coresight_path *path)
{
struct tpdm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

@@ -497,6 +497,7 @@ static int tpdm_enable(struct coresight_device *csdev, struct perf_event *event,
}

__tpdm_enable(drvdata);
+ drvdata->traceid = path->trace_id;
drvdata->enable = true;
spin_unlock(&drvdata->spinlock);

@@ -693,6 +694,29 @@ static struct attribute_group tpdm_attr_grp = {
.attrs = tpdm_attrs,
};

+static ssize_t traceid_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ unsigned long val;
+ struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+ if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
+ return -EINVAL;
+
+ val = drvdata->traceid;
+ return sysfs_emit(buf, "%#lx\n", val);
+}
+static DEVICE_ATTR_RO(traceid);
+
+static struct attribute *traceid_attrs[] = {
+ &dev_attr_traceid.attr,
+ NULL,
+};
+
+static struct attribute_group traceid_attr_grp = {
+ .attrs = traceid_attrs,
+};
+
static ssize_t dsb_mode_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -1367,6 +1391,12 @@ static const struct attribute_group *tpdm_attr_grps[] = {
&tpdm_cmb_patt_grp,
&tpdm_cmb_msr_grp,
&tpdm_mcmb_attr_grp,
+ &traceid_attr_grp,
+ NULL,
+};
+
+static const struct attribute_group *static_tpdm_attr_grps[] = {
+ &traceid_attr_grp,
NULL,
};

@@ -1425,6 +1455,8 @@ static int tpdm_probe(struct device *dev, struct resource *res)
desc.access = CSDEV_ACCESS_IOMEM(base);
if (res)
desc.groups = tpdm_attr_grps;
+ else
+ desc.groups = static_tpdm_attr_grps;
drvdata->csdev = coresight_register(&desc);
if (IS_ERR(drvdata->csdev))
return PTR_ERR(drvdata->csdev);
diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/drivers/hwtracing/coresight/coresight-tpdm.h
index 2867f3ab8186..11da64e1ade8 100644
--- a/drivers/hwtracing/coresight/coresight-tpdm.h
+++ b/drivers/hwtracing/coresight/coresight-tpdm.h
@@ -300,6 +300,7 @@ struct cmb_dataset {
* @cmb Specifics associated to TPDM CMB.
* @dsb_msr_num Number of MSR supported by DSB TPDM
* @cmb_msr_num Number of MSR supported by CMB TPDM
+ * @traceid Trace ID of the path.
*/

struct tpdm_drvdata {
@@ -313,6 +314,7 @@ struct tpdm_drvdata {
struct cmb_dataset *cmb;
u32 dsb_msr_num;
u32 cmb_msr_num;
+ u8 traceid;
};

/* Enumerate members of various datasets */

---
base-commit: b84a0ebe421ca56995ff78b66307667b62b3a900
change-id: 20260316-add-traceid-show-for-tpdm-88d040651f00

Best regards,
--
Jie Gan <jie.gan@oss.qualcomm.com>