[PATCH V3] coresight: Make sysFS functional on topologies with per core sink

[Linu Cherian]

Coresight driver assumes sink is common across all the ETMs,
and tries to build a path between ETM and the first enabled
sink found using bus based search. This breaks sysFS usage
on implementations that has multiple per core sinks in
enabled state.

For this,
- coresight_find_sink API is updated with an additional flag
  so that it is able to return an enabled sink
- coresight_get_enabled_sink API is updated to do a
  connection based search, when a source reference is given.

Signed-off-by: Linu Cherian <lcherian at marvell.com>
---
Applies on https://git.linaro.org/kernel/coresight.git/log/?h=next

Changes in V3:
Fixed checkpatch issue.

 .../hwtracing/coresight/coresight-etm-perf.c  |  2 +-
 drivers/hwtracing/coresight/coresight-priv.h  |  5 +-
 drivers/hwtracing/coresight/coresight.c       | 51 +++++++++++++++++--
 3 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 1a3169e69bb1..25041d2654e3 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -223,7 +223,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		id = (u32)event->attr.config2;
 		sink = coresight_get_sink_by_id(id);
 	} else {
-		sink = coresight_get_enabled_sink(true);
+		sink = coresight_get_enabled_sink(NULL, true);
 	}
 
 	mask = &event_data->mask;
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index f2dc625ea585..010ed26db340 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -148,10 +148,13 @@ static inline void coresight_write_reg_pair(void __iomem *addr, u64 val,
 void coresight_disable_path(struct list_head *path);
 int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data);
 struct coresight_device *coresight_get_sink(struct list_head *path);
-struct coresight_device *coresight_get_enabled_sink(bool reset);
+struct coresight_device *
+coresight_get_enabled_sink(struct coresight_device *source, bool reset);
 struct coresight_device *coresight_get_sink_by_id(u32 id);
 struct coresight_device *
 coresight_find_default_sink(struct coresight_device *csdev);
+struct coresight_device *
+coresight_find_enabled_sink(struct coresight_device *csdev);
 struct list_head *coresight_build_path(struct coresight_device *csdev,
 				       struct coresight_device *sink);
 void coresight_release_path(struct list_head *path);
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index e9c90f2de34a..ae69169c58d3 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -566,6 +566,10 @@ static int coresight_enabled_sink(struct device *dev, const void *data)
 
 /**
  * coresight_get_enabled_sink - returns the first enabled sink found on the bus
+ * When a source reference is given, enabled sink is found using connection based
+ * search.
+ *
+ * @source: Coresight source device reference
  * @deactivate:	Whether the 'enable_sink' flag should be reset
  *
  * When operated from perf the deactivate parameter should be set to 'true'.
@@ -576,10 +580,21 @@ static int coresight_enabled_sink(struct device *dev, const void *data)
  * parameter should be set to 'false', hence mandating users to explicitly
  * clear the flag.
  */
-struct coresight_device *coresight_get_enabled_sink(bool deactivate)
+struct coresight_device *
+coresight_get_enabled_sink(struct coresight_device *source, bool deactivate)
 {
 	struct device *dev = NULL;
+	struct coresight_device *sink;
+
+	if (!source)
+		goto bus_search;
+	sink = coresight_find_enabled_sink(source);
+	if (sink && deactivate)
+		sink->activated = false;
+
+	return sink;
 
+bus_search:
 	dev = bus_find_device(&coresight_bustype, NULL, &deactivate,
 			      coresight_enabled_sink);
 
@@ -828,6 +843,7 @@ coresight_select_best_sink(struct coresight_device *sink, int *depth,
  *
  * @csdev: source / current device to check.
  * @depth: [in] search depth of calling dev, [out] depth of found sink.
+ * @enabled: flag to search only enabled sinks
  *
  * This will walk the connection path from a source (ETM) till a suitable
  * sink is encountered and return that sink to the original caller.
@@ -839,7 +855,7 @@ coresight_select_best_sink(struct coresight_device *sink, int *depth,
  * return best sink found, or NULL if not found at this node or child nodes.
  */
 static struct coresight_device *
-coresight_find_sink(struct coresight_device *csdev, int *depth)
+coresight_find_sink(struct coresight_device *csdev, int *depth, bool enabled)
 {
 	int i, curr_depth = *depth + 1, found_depth = 0;
 	struct coresight_device *found_sink = NULL;
@@ -862,7 +878,8 @@ coresight_find_sink(struct coresight_device *csdev, int *depth)
 
 		child_dev = csdev->pdata->conns[i].child_dev;
 		if (child_dev)
-			sink = coresight_find_sink(child_dev, &child_depth);
+			sink = coresight_find_sink(child_dev, &child_depth,
+						   enabled);
 
 		if (sink)
 			found_sink = coresight_select_best_sink(found_sink,
@@ -872,6 +889,10 @@ coresight_find_sink(struct coresight_device *csdev, int *depth)
 	}
 
 return_def_sink:
+	/* Check if we need to return an enabled sink */
+	if (enabled && found_sink)
+		if (!found_sink->activated)
+			found_sink = NULL;
 	/* return found sink and depth */
 	if (found_sink)
 		*depth = found_depth;
@@ -901,10 +922,30 @@ coresight_find_default_sink(struct coresight_device *csdev)
 
 	/* look for a default sink if we have not found for this device */
 	if (!csdev->def_sink)
-		csdev->def_sink = coresight_find_sink(csdev, &depth);
+		csdev->def_sink = coresight_find_sink(csdev, &depth, false);
 	return csdev->def_sink;
 }
 
+/**
+ * coresight_find_enabled_sink: Find the suitable enabled sink
+ *
+ * @csdev: starting source to find a connected sink.
+ *
+ * Walks connections graph looking for a suitable sink to enable for the
+ * supplied source. Uses CoreSight device subtypes and distance from source
+ * to select the best sink.
+ *
+ * Used in cases where the CoreSight user (sysfs) has selected a sink.
+ */
+struct coresight_device *
+coresight_find_enabled_sink(struct coresight_device *csdev)
+{
+	int depth = 0;
+
+	/* look for the enabled sink */
+	return coresight_find_sink(csdev, &depth, true);
+}
+
 static int coresight_remove_sink_ref(struct device *dev, void *data)
 {
 	struct coresight_device *sink = data;
@@ -992,7 +1033,7 @@ int coresight_enable(struct coresight_device *csdev)
 	 * Search for a valid sink for this session but don't reset the
 	 * "enable_sink" flag in sysFS.  Users get to do that explicitly.
 	 */
-	sink = coresight_get_enabled_sink(false);
+	sink = coresight_get_enabled_sink(csdev, false);
 	if (!sink) {
 		ret = -EINVAL;
 		goto out;
-- 
2.25.1