Re: [PATCH] coresight: fix trace ID search skipping pass-through NoC devices

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

On 9/2/2026 4:22 PM, Leo Yan wrote:
> Hi Jie,
> 
> On Mon, Aug 17, 2026 at 04:50:15PM +0800, Jie Gan wrote:
> 
> [...]
> 
>> @@ -953,8 +953,12 @@ int coresight_path_assign_trace_id(struct coresight_path *path,
>>   		/* Assign a trace ID to the path for the first device that wants to do it */
>>   		trace_id = coresight_get_trace_id(nd->csdev, mode, sink);
>>   
>> -		/* 0 means the device has no ID assignment, so keep searching */
>> -		if (trace_id == 0)
>> +		/*
>> +		 * 0 means the device has no ID assignment, and -EOPNOTSUPP
>> +		 * means the device explicitly declines to assign one (e.g. a
>> +		 * pass-through NoC) - in both cases keep searching downstream.
>> +		 */
>> +		if (trace_id == 0 || trace_id == -EOPNOTSUPP)
>>   			continue;
> 
> Based on IS_VALID_CS_TRACE_ID(), I see 0 is for no ID assignment,
> could you improve a bit tnoc.c instead?
> 
> If so, We don't need to add a new error for the same purpose.
> 

Hi Leo,

Thanks for the suggestion.

I will fix this in the TNOC driver. I agree that there is no need to use 
additional error codes to report the failure.

I will post the new fix patch after below patch[1] to be applied to 
avoid conflict.

[1] 
https://lore.kernel.org/all/20260710-fix-tracenoc-probe-issue-v6-2-41eb36fef8d9@oss.qualcomm.com/

Thanks,
Jie

> ---8<---
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tnoc.c b/drivers/hwtracing/coresight/coresight-tnoc.c
> index 9e8de4323d28..bf221c1e5c48 100644
> --- a/drivers/hwtracing/coresight/coresight-tnoc.c
> +++ b/drivers/hwtracing/coresight/coresight-tnoc.c
> @@ -51,8 +51,8 @@ static void trace_noc_enable_hw(struct trace_noc_drvdata *drvdata)
>   {
>          u32 val;
> 
> -       /* No valid ATID, simply enable the unit */
> -       if (drvdata->atid == -EOPNOTSUPP) {
> +       /* 0 means no ID assignment, simply enable the unit */
> +       if (!drvdata->atid) {
>                  writel(TRACE_NOC_CTRL_PORTEN, drvdata->base + TRACE_NOC_CTRL);
>                  return;
>          }
> @@ -130,10 +130,8 @@ static int trace_noc_init_default_data(struct trace_noc_drvdata *drvdata)
>   {
>          int atid;
> 
> -       if (!dev_is_amba(drvdata->dev)) {
> -               drvdata->atid = -EOPNOTSUPP;
> +       if (!dev_is_amba(drvdata->dev))
>                  return 0;
> -       }
> 
>          atid = coresight_trace_id_get_system_id();
>          if (atid < 0)