Commit 0336bdfd authored by Mike Leach's avatar Mike Leach Committed by Greg Kroah-Hartman
Browse files

coresight: Add default sink selection to CoreSight base 



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: default avatarMike Leach <mike.leach@linaro.org>
Suggested-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: default avatarLeo Yan <leo.yan@linaro.org>
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200716175746.3338735-15-mathieu.poirier@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d021f5c5

drivers/hwtracing/coresight/coresight-priv.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

drivers/hwtracing/coresight/coresight.c

+166 −0
Original line number Diff line number Diff line
@@ -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);

}

include/linux/coresight.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */

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