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

[Jie Gan]

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.

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 <jie.gan@xxxxxxxxxxxxxxxx>
---
 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,
-- 
Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>