linux-kernel - [PATCH 3/7] perf cs-etm: Make a helper to find the Coresight evsel

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Message-Id: <20251201-james-perf-config-bits-v1-3-22ecbbf8007c@linaro.org>
Date: Mon, 01 Dec 2025 16:41:06 +0000
From: James Clark <james.clark@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
 Adrian Hunter <adrian.hunter@...el.com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>, 
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH 3/7] perf cs-etm: Make a helper to find the Coresight evsel

This pattern occurs a few times and we'll add another one later, so add
a helper function for it.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 tools/perf/arch/arm/util/cs-etm.c | 50 +++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 23 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index ea891d12f8f4..22c6272e8c36 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -302,6 +302,19 @@ static int cs_etm_set_sink_attr(struct perf_pmu *pmu,
 	return 0;
 }
 
+static struct evsel *cs_etm_get_evsel(struct evlist *evlist,
+				      struct perf_pmu *cs_etm_pmu)
+{
+	struct evsel *evsel;
+
+	evlist__for_each_entry(evlist, evsel) {
+		if (evsel->core.attr.type == cs_etm_pmu->type)
+			return evsel;
+	}
+
+	return NULL;
+}
+
 static int cs_etm_recording_options(struct auxtrace_record *itr,
 				    struct evlist *evlist,
 				    struct record_opts *opts)
@@ -476,29 +489,21 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
 
 static u64 cs_etm_get_config(struct auxtrace_record *itr)
 {
-	u64 config = 0;
 	struct cs_etm_recording *ptr =
 			container_of(itr, struct cs_etm_recording, itr);
 	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
 	struct evlist *evlist = ptr->evlist;
-	struct evsel *evsel;
+	struct evsel *evsel = cs_etm_get_evsel(evlist, cs_etm_pmu);
 
-	evlist__for_each_entry(evlist, evsel) {
-		if (evsel->core.attr.type == cs_etm_pmu->type) {
-			/*
-			 * Variable perf_event_attr::config is assigned to
-			 * ETMv3/PTM.  The bit fields have been made to match
-			 * the ETMv3.5 ETRMCR register specification.  See the
-			 * PMU_FORMAT_ATTR() declarations in
-			 * drivers/hwtracing/coresight/coresight-perf.c for
-			 * details.
-			 */
-			config = evsel->core.attr.config;
-			break;
-		}
-	}
-
-	return config;
+	/*
+	 * Variable perf_event_attr::config is assigned to
+	 * ETMv3/PTM.  The bit fields have been made to match
+	 * the ETMv3.5 ETRMCR register specification.  See the
+	 * PMU_FORMAT_ATTR() declarations in
+	 * drivers/hwtracing/coresight/coresight-perf.c for
+	 * details.
+	 */
+	return evsel ? evsel->core.attr.config : 0;
 }
 
 #ifndef BIT
@@ -832,12 +837,11 @@ static int cs_etm_snapshot_start(struct auxtrace_record *itr)
 {
 	struct cs_etm_recording *ptr =
 			container_of(itr, struct cs_etm_recording, itr);
-	struct evsel *evsel;
+	struct evsel *evsel = cs_etm_get_evsel(ptr->evlist, ptr->cs_etm_pmu);
+
+	if (evsel)
+		return evsel__disable(evsel);
 
-	evlist__for_each_entry(ptr->evlist, evsel) {
-		if (evsel->core.attr.type == ptr->cs_etm_pmu->type)
-			return evsel__disable(evsel);
-	}
 	return -EINVAL;
 }
 

-- 
2.34.1