Adds a method to select a suitable sink connected to a given source.
In cases where no sink is defined, the coresight_find_default_sink
routine can search from a given source, through the child connections
until a suitable sink is found.
The suitability is defined in by the sink coresight_dev_subtype on the
CoreSight device, and the distance from the source by counting
connections.
Higher value subtype is preferred - where these are equal, shorter
distance from source is used as a tie-break.
This allows for default sink to be discovered were none is specified
(e.g. perf command line)
Signed-off-by: Mike Leach <mike.leach@xxxxxxxxxx>
Suggested-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Reviewed-by: Leo Yan <leo.yan@xxxxxxxxxx>
Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
---
drivers/hwtracing/coresight/coresight-priv.h | 2 +
drivers/hwtracing/coresight/coresight.c | 166 +++++++++++++++++++
include/linux/coresight.h | 3 +
3 files changed, 171 insertions(+)
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 36c943ae94d5..f2dc625ea585 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -150,6 +150,8 @@ 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_sink_by_id(u32 id);
+struct coresight_device *
+coresight_find_default_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 f3efbb3b2b4d..e9c90f2de34a 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -769,6 +769,171 @@ void coresight_release_path(struct list_head *path)
path = NULL;
}
+/* return true if the device is a suitable type for a default sink */
+static inline bool coresight_is_def_sink_type(struct coresight_device *csdev)
+{
+ /* sink & correct subtype */
+ if (((csdev->type == CORESIGHT_DEV_TYPE_SINK) ||
+ (csdev->type == CORESIGHT_DEV_TYPE_LINKSINK)) &&
+ (csdev->subtype.sink_subtype >= CORESIGHT_DEV_SUBTYPE_SINK_BUFFER))
+ return true;
+ return false;
+}
+
+/**
+ * coresight_select_best_sink - return the best sink for use as default from
+ * the two provided.
+ *
+ * @sink: current best sink.
+ * @depth: search depth where current sink was found.
+ * @new_sink: new sink for comparison with current sink.
+ * @new_depth: search depth where new sink was found.
+ *
+ * Sinks prioritised according to coresight_dev_subtype_sink, with only
+ * subtypes CORESIGHT_DEV_SUBTYPE_SINK_BUFFER or higher being used.
+ *
+ * Where two sinks of equal priority are found, the sink closest to the
+ * source is used (smallest search depth).
+ *
+ * return @new_sink & update @depth if better than @sink, else return @sink.
+ */
+static struct coresight_device *
+coresight_select_best_sink(struct coresight_device *sink, int *depth,
+ struct coresight_device *new_sink, int new_depth)
+{
+ bool update = false;
+
+ if (!sink) {
+ /* first found at this level */
+ update = true;
+ } else if (new_sink->subtype.sink_subtype >
+ sink->subtype.sink_subtype) {
+ /* found better sink */
+ update = true;
+ } else if ((new_sink->subtype.sink_subtype ==
+ sink->subtype.sink_subtype) &&
+ (*depth > new_depth)) {
+ /* found same but closer sink */
+ update = true;
+ }
+
+ if (update)
+ *depth = new_depth;
+ return update ? new_sink : sink;
+}
+
+/**
+ * coresight_find_sink - recursive function to walk trace connections from
+ * source to find a suitable default sink.
+ *
+ * @csdev: source / current device to check.
+ * @depth: [in] search depth of calling dev, [out] depth of found sink.
+ *
+ * This will walk the connection path from a source (ETM) till a suitable
+ * sink is encountered and return that sink to the original caller.
+ *
+ * If current device is a plain sink return that & depth, otherwise recursively
+ * call child connections looking for a sink. Select best possible using
+ * coresight_select_best_sink.
+ *
+ * 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)
+{
+ int i, curr_depth = *depth + 1, found_depth = 0;
+ struct coresight_device *found_sink = NULL;
+
+ if (coresight_is_def_sink_type(csdev)) {
+ found_depth = curr_depth;
+ found_sink = csdev;
+ if (csdev->type == CORESIGHT_DEV_TYPE_SINK)
+ goto return_def_sink;
+ /* look past LINKSINK for something better */
+ }
+
+ /*
+ * Not a sink we want - or possible child sink may be better.
+ * recursively explore each port found on this element.
+ */
+ for (i = 0; i < csdev->pdata->nr_outport; i++) {
+ struct coresight_device *child_dev, *sink = NULL;
+ int child_depth = curr_depth;
+
+ child_dev = csdev->pdata->conns[i].child_dev;
+ if (child_dev)
+ sink = coresight_find_sink(child_dev, &child_depth);
+
+ if (sink)
+ found_sink = coresight_select_best_sink(found_sink,
+ &found_depth,
+ sink,
+ child_depth);
+ }
+
+return_def_sink:
+ /* return found sink and depth */
+ if (found_sink)
+ *depth = found_depth;
+ return found_sink;
+}
+
+/**
+ * coresight_find_default_sink: Find a sink suitable for use as a
+ * default 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.
+ *
+ * If a sink is found, then the default sink for this device is set and
+ * will be automatically used in future.
+ *
+ * Used in cases where the CoreSight user (perf / sysfs) has not selected a
+ * sink.
+ */
+struct coresight_device *
+coresight_find_default_sink(struct coresight_device *csdev)
+{
+ int depth = 0;
+
+ /* 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);
+ return csdev->def_sink;
+}
+
+static int coresight_remove_sink_ref(struct device *dev, void *data)
+{
+ struct coresight_device *sink = data;
+ struct coresight_device *source = to_coresight_device(dev);
+
+ if (source->def_sink == sink)
+ source->def_sink = NULL;
+ return 0;
+}
+
+/**
+ * coresight_clear_default_sink: Remove all default sink references to the
+ * supplied sink.
+ *
+ * If supplied device is a sink, then check all the bus devices and clear
+ * out all the references to this sink from the coresight_device def_sink
+ * parameter.
+ *
+ * @csdev: coresight sink - remove references to this from all sources.
+ */
+static void coresight_clear_default_sink(struct coresight_device *csdev)
+{
+ if ((csdev->type == CORESIGHT_DEV_TYPE_SINK) ||
+ (csdev->type == CORESIGHT_DEV_TYPE_LINKSINK)) {
+ bus_for_each_dev(&coresight_bustype, NULL, csdev,
+ coresight_remove_sink_ref);
+ }
+}
+
/** coresight_validate_source - make sure a source has the right credentials
* @csdev: the device structure for a source.
* @function: the function this was called from.
@@ -1358,6 +1523,7 @@ void coresight_unregister(struct coresight_device *csdev)
etm_perf_del_symlink_sink(csdev);
/* Remove references of that device in the topology */
coresight_remove_conns(csdev);
+ coresight_clear_default_sink(csdev);
coresight_release_platform_data(csdev, csdev->pdata);
device_unregister(&csdev->dev);
}
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 84dc695e87d4..58fffdecdbfd 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -48,6 +48,7 @@ enum coresight_dev_subtype_sink {
CORESIGHT_DEV_SUBTYPE_SINK_NONE,
CORESIGHT_DEV_SUBTYPE_SINK_PORT,
CORESIGHT_DEV_SUBTYPE_SINK_BUFFER,
+ CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM,
};
enum coresight_dev_subtype_link {
@@ -182,6 +183,7 @@ struct coresight_sysfs_link {
* happens when a source has been selected and a path is enabled
* from source to that sink.
* @ea: Device attribute for sink representation under PMU directory.
+ * @def_sink: cached reference to default sink found for this device.
* @ect_dev: Associated cross trigger device. Not part of the trace data
* path or connections.
* @nr_links: number of sysfs links created to other components from this
@@ -200,6 +202,7 @@ struct coresight_device {
/* sink specific fields */
bool activated; /* true only if a sink is part of a path */
struct dev_ext_attribute *ea;
+ struct coresight_device *def_sink;
/* cross trigger handling */
struct coresight_device *ect_dev;
/* sysfs links between components */
--
2.17.1
