[PATCH v2] coresight: tnoc: fix trace ID path assignment failure on non-AMBA tnoc

[Leo Yan]

On Wed, Sep 02, 2026 at 05:41:43PM +0800, Jie Gan wrote:
> For a tnoc device not on the AMBA bus, atid was set to -EOPNOTSUPP.
> trace_noc_id() returns this value directly to
> coresight_path_assign_trace_id(), which only treats a literal 0
> return as "this device has no ID, keep searching the path" -
> any other value is checked against IS_VALID_CS_TRACE_ID() and
> rejected. A negative atid therefore made path assignment fail with
> -EINVAL instead of falling through to the next device in the path
> that could supply a valid trace ID.
> 
> Use 0, the same sentinel coresight_path_assign_trace_id() already
> recognizes as "not allocated", instead of -EOPNOTSUPP.
> 
> Fixes: 5799dee92dc2 ("coresight-tnoc: add platform driver to support Interconnect TNOC")
> Signed-off-by: Jie Gan <jie.gan at oss.qualcomm.com>

Reviewed-by: Leo Yan <leo.yan at arm.com>