linux-kernel - [PATCH v1 6/8] coresight: perf: Update buffer on AUX pause

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Message-Id: <20250224151423.1630639-7-leo.yan@arm.com>
Date: Mon, 24 Feb 2025 15:14:21 +0000
From: Leo Yan <leo.yan@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	James Clark <james.clark@...aro.org>,
	Jonathan Corbet <corbet@....net>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Leo Yan <leo.yan@....com>
Subject: [PATCH v1 6/8] coresight: perf: Update buffer on AUX pause

Due to sinks like ETR and ETB don't support interrupt handling, the
hardware trace data might be lost for continuous running tasks.

This commit takes advantage of the AUX pause for updating trace buffer
to mitigate the trace data losing issue.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 .../hwtracing/coresight/coresight-etm-perf.c  | 38 ++++++++++++++++++-
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index d759663a1f7d..667110429de9 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -594,14 +594,48 @@ static void etm_event_start(struct perf_event *event, int flags)
 	return;
 }
 
-static void etm_event_pause(struct coresight_device *csdev,
+static void etm_event_pause(struct perf_event *event,
+			    struct coresight_device *csdev,
 			    struct etm_ctxt *ctxt)
 {
+	int cpu = smp_processor_id();
+	struct coresight_device *sink;
+	struct perf_output_handle *handle = &ctxt->handle;
+	struct list_head *path;
+	unsigned long size;
+
 	if (!ctxt->event_data)
 		return;
 
 	/* Stop tracer */
 	coresight_pause_source(csdev);
+
+	/* Bail out if no need update buffer */
+	if (!ctxt->event_data->update_buf_on_pause)
+		return;
+
+	if (WARN_ON_ONCE(handle->event != event))
+		return;
+
+	path = etm_event_cpu_path(ctxt->event_data, cpu);
+	sink = coresight_get_sink(path);
+	if (WARN_ON_ONCE(!sink))
+		return;
+
+	if (!sink_ops(sink)->update_buffer)
+		return;
+
+	size = sink_ops(sink)->update_buffer(sink, handle,
+					     ctxt->event_data->snk_config);
+	if (READ_ONCE(handle->event)) {
+		if (!size)
+			return;
+
+		perf_aux_output_end(handle, size);
+		perf_aux_output_begin(handle, event);
+	} else {
+		WARN_ON_ONCE(size);
+	}
 }
 
 static void etm_event_stop(struct perf_event *event, int mode)
@@ -615,7 +649,7 @@ static void etm_event_stop(struct perf_event *event, int mode)
 	struct list_head *path;
 
 	if (mode & PERF_EF_PAUSE)
-		return etm_event_pause(csdev, ctxt);
+		return etm_event_pause(event, csdev, ctxt);
 
 	/*
 	 * If we still have access to the event_data via handle,
-- 
2.34.1