Optimize the Coresight Trace id allocation logic

drivers/hwtracing/coresight/coresight-core.c

@@ -792,8 +792,8 @@ 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;
@@ -804,14 +804,21 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
 		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.
+		 * 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) {
-			path->trace_id = trace_id;
-			return;
-		}
+		if (trace_id == 0 || trace_id == -EOPNOTSUPP)
+			continue;
+
+		if (!IS_VALID_CS_TRACE_ID(trace_id))
+			return -EINVAL;
+
+		path->trace_id = trace_id;
+		return 0;
 	}
+
+	return -EINVAL;
 }
 
 /**

drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -321,6 +321,7 @@ 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)
@@ -418,8 +419,8 @@ 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;

drivers/hwtracing/coresight/coresight-priv.h

@@ -154,7 +154,7 @@ 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);
 int coresight_get_in_port_dest(struct coresight_device *src,
 			       struct coresight_device *dest);

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, NULL);