linux-kernel - [PATCH 08/19] coresight: trbe: Use PERF_AUX_FLAG_PARTIAL instead of PERF_AUX_FLAG

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Message-Id: <20251201-trbe_buffer_refactor_v1-1-v1-8-7da32b076b28@arm.com>
Date: Mon, 01 Dec 2025 11:21:58 +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>, 
 Anshuman Khandual <anshuman.khandual@....com>, 
 Yeoreum Yun <yeoreum.yun@....com>, Will Deacon <will@...nel.org>, 
 Mark Rutland <mark.rutland@....com>, Tamas Petz <tamas.petz@....com>, 
 Tamas Zsoldos <tamas.zsoldos@....com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
 Leo Yan <leo.yan@....com>
Subject: [PATCH 08/19] coresight: trbe: Use PERF_AUX_FLAG_PARTIAL instead
 of PERF_AUX_FLAG_COLLISION

When tracing stops, there is no collision with other samples, so using
PERF_AUX_FLAG_COLLISION does not accurately reflect the trace state and
may mislead userspace.

Use PERF_AUX_FLAG_PARTIAL instead to indicate that tracing stopped and
the record may contain gaps.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 drivers/hwtracing/coresight/coresight-trbe.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index b06885a08e082fd34f68d9588518807b5c47c86e..0caa4a6b437a3aa39fc6bcc72a23711b54f7c598 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -669,21 +669,14 @@ static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *hand
 	}
 
 	/*
-	 * Mark the buffer to indicate that there was a WRAP event by
-	 * setting the COLLISION flag. This indicates to the user that
-	 * the TRBE trace collection was stopped without stopping the
-	 * ETE and thus there might be some amount of trace that was
-	 * lost between the time the WRAP was detected and the IRQ
-	 * was consumed by the CPU.
-	 *
-	 * Setting the TRUNCATED flag would move the event to STOPPED
-	 * state unnecessarily, even when there is space left in the
-	 * ring buffer. Using the COLLISION flag doesn't have this side
-	 * effect. We only set TRUNCATED flag when there is no space
-	 * left in the ring buffer.
+	 * Mark the buffer to indicate that the trace is stopped by setting
+	 * the PARTIAL flag. This indicates to the user that the TRBE trace
+	 * collection was stopped without stopping the ETE and thus there
+	 * might be some amount of trace that was lost between the time the
+	 * TRBE event was detected and the IRQ was consumed by the CPU.
 	 */
 	if (!is_trbe_running(trbsr))
-		perf_aux_output_flag(handle, PERF_AUX_FLAG_COLLISION);
+		perf_aux_output_flag(handle, PERF_AUX_FLAG_PARTIAL);
 
 	if (is_trbe_wrap(trbsr))
 		return TRBE_FAULT_ACT_WRAP;

-- 
2.34.1