[PATCH 6/6] coresight: perf: Retry failed HW_ID writes

[James Clark]

Don't set the aux_hwid_done bit when writes fail so that it can be
retried later if the ring buffer was full.

Add a second attempt on stop in case this session only has one call
to start. Otherwise there is no chance to retry and it isn't fixed by
not setting aux_hwid_done.

Signed-off-by: James Clark <james.clark at linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 52 +++++++++++++++---------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 09b21a711a87..0ffc5cd9c88f 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -536,6 +536,31 @@ static int etm_event_resume(struct coresight_path *path)
 	return ret;
 }
 
+static void etm_output_hw_id(struct perf_event *event,
+			     struct etm_event_data *event_data,
+			     struct coresight_path *path,
+			     struct coresight_device *sink)
+{
+	int cpu = smp_processor_id();
+	u64 hw_id;
+
+	/*
+	 * output cpu / trace ID in perf record, once for the lifetime
+	 * of the event.
+	 */
+	if (!cpumask_test_cpu(cpu, &event_data->aux_hwid_done)) {
+		hw_id = FIELD_PREP(CS_AUX_HW_ID_MAJOR_VERSION_MASK,
+				CS_AUX_HW_ID_MAJOR_VERSION);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_MINOR_VERSION_MASK,
+				CS_AUX_HW_ID_MINOR_VERSION);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK, path->trace_id);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_SINK_ID_MASK, coresight_get_sink_id(sink));
+
+		if (!perf_report_aux_output_id(event, hw_id))
+			cpumask_set_cpu(cpu, &event_data->aux_hwid_done);
+	}
+}
+
 static void etm_event_start(struct perf_event *event, int flags)
 {
 	int cpu = smp_processor_id();
@@ -544,7 +569,6 @@ static void etm_event_start(struct perf_event *event, int flags)
 	struct perf_output_handle *handle = &ctxt->handle;
 	struct coresight_device *source, *sink;
 	struct coresight_path *path;
-	u64 hw_id;
 
 	if (flags & PERF_EF_RESUME) {
 		path = etm_event_get_ctxt_path(ctxt);
@@ -596,22 +620,7 @@ static void etm_event_start(struct perf_event *event, int flags)
 	if (coresight_enable_source(source, event, CS_MODE_PERF, path))
 		goto fail_disable_path;
 
-	/*
-	 * output cpu / trace ID in perf record, once for the lifetime
-	 * of the event.
-	 */
-	if (!cpumask_test_cpu(cpu, &event_data->aux_hwid_done)) {
-		cpumask_set_cpu(cpu, &event_data->aux_hwid_done);
-
-		hw_id = FIELD_PREP(CS_AUX_HW_ID_MAJOR_VERSION_MASK,
-				CS_AUX_HW_ID_MAJOR_VERSION);
-		hw_id |= FIELD_PREP(CS_AUX_HW_ID_MINOR_VERSION_MASK,
-				CS_AUX_HW_ID_MINOR_VERSION);
-		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK, path->trace_id);
-		hw_id |= FIELD_PREP(CS_AUX_HW_ID_SINK_ID_MASK, coresight_get_sink_id(sink));
-
-		perf_report_aux_output_id(event, hw_id);
-	}
+	etm_output_hw_id(event, event_data, path, sink);
 
 out:
 	/* Tell the perf core the event is alive */
@@ -630,7 +639,7 @@ static void etm_event_start(struct perf_event *event, int flags)
 	 */
 	if (READ_ONCE(handle->event)) {
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
-		perf_aux_output_end(handle, 0);
+		perf_aux_output_end(path->handle, 0);
 	}
 fail:
 	event->hw.state = PERF_HES_STOPPED;
@@ -679,6 +688,7 @@ static void etm_event_pause(struct coresight_path *path,
 		if (!size)
 			return;
 
+		etm_output_hw_id(event, event_data, path, sink);
 		perf_aux_output_end(handle, size);
 		perf_aux_output_begin(handle, event);
 	} else {
@@ -769,10 +779,12 @@ static void etm_event_stop(struct perf_event *event, int mode)
 		 * But we should never get a non-zero size with
 		 * an invalid handle.
 		 */
-		if (READ_ONCE(handle->event))
+		if (READ_ONCE(handle->event)) {
+			etm_output_hw_id(event, event_data, path, sink);
 			perf_aux_output_end(handle, size);
-		else
+		} else {
 			WARN_ON(size);
+		}
 	}
 
 	/* Disabling the path make its elements available to other sessions */

-- 
2.43.0