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

[Jie Gan <jie.gan@oss.qualcomm.com>]

Hi Suzuki,

On 3/16/2026 5:32 PM, Suzuki K Poulose wrote:
> 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

It's taking effort to retrieve the trace ID of the TPDA device because 
it's not a source device. The trace ID is required to identify the 
origin of the trace data and is essential for parsing the received data.

> 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

Yes, we dont allocate trace ID for a TPDM device. The TraceID is 
allocated to the TPDA device.

Thanks,
Jie

> 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,
> 
>