[PATCH 1/7] perf: cs-etm: Fix timeless decode mode detection

[James Clark <james.clark@arm.com>]

In this context, timeless refers to the trace data rather than the perf
event data. But when detecting whether there are timestamps in the trace
data or not, the presence of a timestamp flag on any perf event is used.

Since commit f42c0ce573df ("perf record: Always get text_poke events
with --kcore option") timestamps were added to a tracking event when
--kcore is used which breaks this detection mechanism. Fix it by
detecting if trace timestamps exist by looking at the ETM config flags.
This would have always been a more accurate way of doing it anyway.

This fixes the following error message when using --kcore with
Coresight:

  $ perf record --kcore -e cs_etm// --per-thread
  $ perf report
  The perf.data/data data has no samples!

Fixes: f42c0ce573df ("perf record: Always get text_poke events with --kcore option")
Reported-by: Yang Shi <shy828301@gmail.com>
Link: https://lore.kernel.org/lkml/CAHbLzkrJQTrYBtPkf=jf3OpQ-yBcJe7XkvQstX9j2frz4WF-SQ@mail.gmail.com/
Signed-off-by: James Clark <james.clark@arm.com>
---
 tools/perf/util/cs-etm.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 8dd81ddd9e4e..50593289d53c 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -2684,26 +2684,29 @@ static int cs_etm__process_auxtrace_event(struct perf_session *session,
 	return 0;
 }
 
-static bool cs_etm__is_timeless_decoding(struct cs_etm_auxtrace *etm)
+static int cs_etm__setup_timeless_decoding(struct cs_etm_auxtrace *etm)
 {
 	struct evsel *evsel;
 	struct evlist *evlist = etm->session->evlist;
-	bool timeless_decoding = true;
 
 	/* Override timeless mode with user input from --itrace=Z */
-	if (etm->synth_opts.timeless_decoding)
-		return true;
+	if (etm->synth_opts.timeless_decoding) {
+		etm->timeless_decoding = true;
+		return 0;
+	}
 
 	/*
-	 * Circle through the list of event and complain if we find one
-	 * with the time bit set.
+	 * Find the cs_etm evsel and look at what its timestamp setting was
 	 */
-	evlist__for_each_entry(evlist, evsel) {
-		if ((evsel->core.attr.sample_type & PERF_SAMPLE_TIME))
-			timeless_decoding = false;
-	}
+	evlist__for_each_entry(evlist, evsel)
+		if (cs_etm__evsel_is_auxtrace(etm->session, evsel)) {
+			etm->timeless_decoding =
+				!(evsel->core.attr.config & BIT(ETM_OPT_TS));
+			return 0;
+		}
 
-	return timeless_decoding;
+	pr_err("CS ETM: Couldn't find ETM evsel\n");
+	return -EINVAL;
 }
 
 /*
@@ -3155,7 +3158,6 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
 	etm->snapshot_mode = (ptr[CS_ETM_SNAPSHOT] != 0);
 	etm->metadata = metadata;
 	etm->auxtrace_type = auxtrace_info->type;
-	etm->timeless_decoding = cs_etm__is_timeless_decoding(etm);
 
 	/* Use virtual timestamps if all ETMs report ts_source = 1 */
 	etm->has_virtual_ts = cs_etm__has_virtual_ts(metadata, num_cpu);
@@ -3172,6 +3174,10 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
 	etm->auxtrace.evsel_is_auxtrace = cs_etm__evsel_is_auxtrace;
 	session->auxtrace = &etm->auxtrace;
 
+	err = cs_etm__setup_timeless_decoding(etm);
+	if (err)
+		return err;
+
 	etm->unknown_thread = thread__new(999999999, 999999999);
 	if (!etm->unknown_thread) {
 		err = -ENOMEM;
-- 
2.34.1