Re: [PATCH v2] coresight: tpdm: add traceid_show for checking traceid

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 16/03/2026 07:23, Jie Gan wrote:
> 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 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/

Why is this patch required even ? For each TPDM there is a single
port in a single TPDA in the system where it can reach and that is
fixed for a platform. Can we not get this from there ? Also, there
is not TraceID technically for a TPDM, right ? It is all a property
of the TPDA ?

Suzuki


> ---
>   drivers/hwtracing/coresight/coresight-tpdm.c | 31 +++++++++++++++++++++++++++-
>   drivers/hwtracing/coresight/coresight-tpdm.h |  2 ++
>   2 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
> index da77bdaad0a4..774a63def817 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 +694,26 @@ 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);
> +
> +	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 +1388,12 @@ 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 +1452,8 @@ 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..befecbb896f4 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,