coresight: reset "enable_sink" flag when need be

When using coresight from the perf interface sinks are specified
as part of the perf command line.  As such the sink needs to be
disabled once it has been acknowledged by the coresight framework.
Otherwise the sink stays enabled, which may interfere with other
sessions.

This patch removes the sink selection check from the build path
process and make it a function on it's own.  The function is
then used when operating from sysFS or perf to determine what
sink has been selected.

If operated from perf the status of the "enable_sink" flag is
reset so that concurrent session can use a different sink.  When
used from sysFS the status of the flag is left untouched since
users have full control.

The implementation doesn't handle a scenario where a sink has
been enabled from sysFS and another sink is selected from the
perf command line as both modes of operation are mutually
exclusive.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 15 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 2cd7c718198a..5a346fc8ce06 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -202,6 +202,21 @@ static void *etm_setup_aux(int event_cpu, void **pages,
 	if (!event_data)
 		return NULL;
 
+	/*
+	 * In theory nothing prevent tracers in a trace session from being
+	 * associated with different sinks, nor having a sink per tracer.  But
+	 * until we have HW with this kind of topology we need to assume tracers
+	 * in a trace session are using the same sink.  Therefore go through
+	 * the coresight bus and pick the first enabled sink.
+	 *
+	 * When operated from sysFS users are responsible to enable the sink
+	 * while from perf, the perf tools will do it based on the choice made
+	 * on the cmd line.  As such the "enable_sink" flag in sysFS is reset.
+	 */
+	sink = coresight_get_enabled_sink(true);
+	if (!sink)
+		return NULL;
+
 	INIT_WORK(&event_data->work, free_event_data);
 
 	mask = &event_data->mask;
@@ -219,25 +234,11 @@ static void *etm_setup_aux(int event_cpu, void **pages,
 		 * list of devices from source to sink that can be
 		 * referenced later when the path is actually needed.
 		 */
-		event_data->path[cpu] = coresight_build_path(csdev);
+		event_data->path[cpu] = coresight_build_path(csdev, sink);
 		if (IS_ERR(event_data->path[cpu]))
 			goto err;
 	}
 
-	/*
-	 * In theory nothing prevent tracers in a trace session from being
-	 * associated with different sinks, nor having a sink per tracer.  But
-	 * until we have HW with this kind of topology and a way to convey
-	 * sink assignement from the perf cmd line we need to assume tracers
-	 * in a trace session are using the same sink.  Therefore pick the sink
-	 * found at the end of the first available path.
-	 */
-	cpu = cpumask_first(mask);
-	/* Grab the sink at the end of the path */
-	sink = coresight_get_sink(event_data->path[cpu]);
-	if (!sink)
-		goto err;
-
 	if (!sink_ops(sink)->alloc_buffer)
 		goto err;