Re: [PATCH] coresight: fix trace ID search skipping pass-through NoC devices
From: Jie Gan <hidden>
Date: 2026-09-02 06:00:24
Also in:
lkml
On 8/17/2026 4:50 PM, Jie Gan wrote:
coresight_path_assign_trace_id() only treats a trace_id of 0 as "this device has no ID assignment, keep searching downstream". Pass-through NoC links such as itnoc (qcom,coresight-itnoc) intentionally return -EOPNOTSUPP from their .trace_id callback since they have no ATID register to program, but that negative value falls through to the IS_VALID_CS_TRACE_ID() check and is rejected, aborting the whole path with -EINVAL before the real trace ID owner further downstream is ever reached.
Gentle reminder
quoted hunk ↗ jump to hunk
This breaks enabling any source whose path traverses an itnoc, e.g. writing 1 to tpdm/enable_source for a TPDM fails with: sh: write error: Invalid argument Skip devices that return -EOPNOTSUPP the same way as devices that return 0, so the search continues to the next device on the path. Fixes: f4526ffee6ff ("coresight: fix missing error code when trace ID is invalid") Signed-off-by: Jie Gan <redacted> --- drivers/hwtracing/coresight/coresight-core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 6d65c43d574f..949ee9f00097 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c@@ -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; if (!IS_VALID_CS_TRACE_ID(trace_id))--- base-commit: 4477a78374a57c3809b172ad30cceabda48c47c6 change-id: 20260817-fix-trace-id-assign-issue-d269e90d1c62 Best regards,