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

[Jie Gan]

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>
---
Changes in v2:
- fixes the issue in TNOC driver instead of in generic framework.
Link to v1 - https://lore.kernel.org/all/20260817-fix-trace-id-assign-issue-v1-1-b2164e33f9fa@oss.qualcomm.com/
---
 drivers/hwtracing/coresight/coresight-tnoc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tnoc.c b/drivers/hwtracing/coresight/coresight-tnoc.c
index 9e8de4323d28..8924b61ad076 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 == 0) {
 		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)
@@ -166,7 +164,7 @@ static umode_t trace_id_is_visible(struct kobject *kobj,
 	struct device *dev = kobj_to_dev(kobj);
 	struct trace_noc_drvdata *drvdata = dev_get_drvdata(dev->parent);
 
-	if (attr == &dev_attr_traceid.attr && drvdata->atid < 0)
+	if (attr == &dev_attr_traceid.attr && drvdata->atid == 0)
 		return 0;
 
 	return attr->mode;

---
base-commit: 8b72f6626dc39b9e7e82b2721d4f7c3b86286012
change-id: 20260902-fix-trace-id-error-in-tnoc-driver-eda88ea30662

Best regards,
-- 
Jie Gan <jie.gan at oss.qualcomm.com>