[PATCH v4] coresight: fix missing error code when trace ID is invalid

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

When coresight_path_assign_trace_id() cannot assign a valid trace ID,
coresight_enable_sysfs() takes the err_path goto with ret still 0,
returning success to the caller despite no trace session being started.

Change coresight_path_assign_trace_id() to return int, moving the
IS_VALID_CS_TRACE_ID() check inside it so it returns -EINVAL on failure
and 0 on success. Update both callers to propagate this return value
directly instead of inspecting path->trace_id after the call.

Fixes: d87d76d823d1 ("Coresight: Allocate trace ID after building the path")
Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Richard Cheng <icheng@nvidia.com>
Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
---
Changes in v4:
- Refactor the coresight_path_assign_trace_id according to Leo's suggestion.
- Link to v3: https://lore.kernel.org/r/20260511-fix-trace-id-error-v3-1-ac4c8356efff@oss.qualcomm.com

Changes in v3:
- directly return the value for clear expression.
- Link to v2: https://lore.kernel.org/r/20260509-fix-trace-id-error-v2-1-c900bcbab3e9@oss.qualcomm.com

Changes in v2:
- Refactor the coresight_path_assign_trace_id function.
- Link to v1: https://lore.kernel.org/r/20260508-fix-trace-id-error-v1-1-5f11a5456fdf@oss.qualcomm.com
---
 drivers/hwtracing/coresight/coresight-core.c     | 23 +++++++++++++----------
 drivers/hwtracing/coresight/coresight-etm-perf.c |  5 +++--
 drivers/hwtracing/coresight/coresight-priv.h     |  2 +-
 drivers/hwtracing/coresight/coresight-sysfs.c    |  4 ++--
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 46f247f73cf6..2105bb813940 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -739,8 +739,8 @@ static int coresight_get_trace_id(struct coresight_device *csdev,
  * Call this after creating the path and before enabling it. This leaves
  * the trace ID set on the path, or it remains 0 if it couldn't be assigned.
  */
-void coresight_path_assign_trace_id(struct coresight_path *path,
-				    enum cs_mode mode)
+int coresight_path_assign_trace_id(struct coresight_path *path,
+				   enum cs_mode mode)
 {
 	struct coresight_device *sink = coresight_get_sink(path);
 	struct coresight_node *nd;
@@ -750,15 +750,18 @@ void 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 in this context is that it didn't want to assign so keep searching.
-		 * Non 0 is either success or fail.
-		 */
-		if (trace_id != 0) {
-			path->trace_id = trace_id;
-			return;
-		}
+		/* 0 means the device has no ID assignment, so keep searching */
+		if (trace_id == 0)
+			continue;
+
+		if (!IS_VALID_CS_TRACE_ID(trace_id))
+			return -EINVAL;
+
+		path->trace_id = trace_id;
+		return 0;
 	}
+
+	return -EINVAL;
 }
 
 /**
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index f85dedf89a3f..89ba7c9a6613 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -324,6 +324,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 	struct coresight_device *sink = NULL;
 	struct coresight_device *user_sink = NULL, *last_sink = NULL;
 	struct etm_event_data *event_data = NULL;
+	int ret;
 
 	event_data = alloc_event_data(cpu);
 	if (!event_data)
@@ -420,8 +421,8 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		}
 
 		/* ensure we can allocate a trace ID for this CPU */
-		coresight_path_assign_trace_id(path, CS_MODE_PERF);
-		if (!IS_VALID_CS_TRACE_ID(path->trace_id)) {
+		ret = coresight_path_assign_trace_id(path, CS_MODE_PERF);
+		if (ret) {
 			cpumask_clear_cpu(cpu, mask);
 			coresight_release_path(path);
 			continue;
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 1ea882dffd70..34c7e792adbd 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -153,7 +153,7 @@ int coresight_make_links(struct coresight_device *orig,
 void coresight_remove_links(struct coresight_device *orig,
 			    struct coresight_connection *conn);
 u32 coresight_get_sink_id(struct coresight_device *csdev);
-void coresight_path_assign_trace_id(struct coresight_path *path,
+int coresight_path_assign_trace_id(struct coresight_path *path,
 				   enum cs_mode mode);
 
 #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
index d2a6ed8bcc74..b6a870399e83 100644
--- a/drivers/hwtracing/coresight/coresight-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-sysfs.c
@@ -211,8 +211,8 @@ int coresight_enable_sysfs(struct coresight_device *csdev)
 		goto out;
 	}
 
-	coresight_path_assign_trace_id(path, CS_MODE_SYSFS);
-	if (!IS_VALID_CS_TRACE_ID(path->trace_id))
+	ret = coresight_path_assign_trace_id(path, CS_MODE_SYSFS);
+	if (ret)
 		goto err_path;
 
 	ret = coresight_enable_path(path, CS_MODE_SYSFS);

---
base-commit: 17c7841d09ee7d33557fd075562d9289b6018c90
change-id: 20260508-fix-trace-id-error-dbfdd4d8f2d1

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