[PATCH v7 10/20] coresight: Save active path for system tracers

[Leo Yan]

Store the active path in the source device structure for system
tracers (e.g. STM).  Ensure the path pointer is cleared when the
source is disabled.

Tested-by: James Clark <james.clark at linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun at arm.com>
Reviewed-by: James Clark <james.clark at linaro.org>
Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 28 ++++++++++++++++++++++++++--
 include/linux/coresight.h                    |  2 ++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 4b55c54c5fbade99404ad662aa4111d4c3c2b85b..81bf4637f788f99844e839fd9dad8802ee78eb60 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -430,19 +430,43 @@ int coresight_enable_source(struct coresight_device *csdev,
 			    struct perf_event *event, enum cs_mode mode,
 			    struct coresight_path *path)
 {
+	int ret;
+
 	if (!coresight_is_device_source(csdev))
 		return -EINVAL;
 
-	return source_ops(csdev)->enable(csdev, event, mode, path);
+	ret = source_ops(csdev)->enable(csdev, event, mode, path);
+	if (ret)
+		return ret;
+
+	/*
+	 * The per-CPU source has updated its path pointer in the enable()
+	 * callback, ensuring synchronization on the target CPU. Set the
+	 * path pointer here for non per-CPU sources.
+	 */
+	if (!coresight_is_percpu_source(csdev))
+		csdev->path = path;
+
+	return 0;
 }
 
 void coresight_disable_source(struct coresight_device *csdev, void *data)
 {
+	struct coresight_path *path;
+
 	if (!coresight_is_device_source(csdev))
 		return;
 
+	/*
+	 * The per-CPU source's disable callback may clear csdev->path, so
+	 * save the path pointer used by disabling helper.
+	 */
+	path = csdev->path;
 	source_ops(csdev)->disable(csdev, data);
-	coresight_disable_helpers(csdev, NULL);
+	coresight_disable_helpers(csdev, path);
+
+	if (!coresight_is_percpu_source(csdev))
+		csdev->path = NULL;
 }
 EXPORT_SYMBOL_GPL(coresight_disable_source);
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index f771615852b84200e37b844648a13bd18c91593d..11d61cdfac8d4d51e831a84635d8438383665d3e 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -268,6 +268,7 @@ struct coresight_trace_id_map {
  *		spinlock.
  * @orphan:	true if the component has connections that haven't been linked.
  * @cpu:	The CPU this component is affined to (-1 for not CPU bound).
+ * @path:	Activated path pointer (only used for source device).
  * @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs
  *		by writing a 1 to the 'enable_sink' file.  A sink can be
  *		activated but not yet enabled.  Enabling for a _sink_ happens
@@ -295,6 +296,7 @@ struct coresight_device {
 	int refcnt;
 	bool orphan;
 	int cpu;
+	struct coresight_path *path;
 	/* sink specific fields */
 	bool sysfs_sink_activated;
 	struct dev_ext_attribute *ea;

-- 
2.34.1