linux-kernel - [RFC PATCH 5/6] perf cs-etm: Improve Coresight zero timestamp warning

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Message-Id: <20210729155805.2830-6-james.clark@arm.com>
Date:   Thu, 29 Jul 2021 16:58:04 +0100
From:   James Clark <james.clark@....com>
To:     acme@...nel.org, mathieu.poirier@...aro.org,
        coresight@...ts.linaro.org, linux-perf-users@...r.kernel.org
Cc:     leo.yan@...aro.org, suzuki.poulose@....com, mike.leach@...aro.org,
        James Clark <james.clark@....com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [RFC PATCH 5/6] perf cs-etm: Improve Coresight zero timestamp warning

Only show the warning if the user hasn't already set timeless mode and
improve the text because there was ambiguity around the meaning of '...'

Change the warning to a UI warning instead of printing straight to
stderr because this corrupts the UI when perf report TUI is used. The UI
warning function also handles printing to stderr when in perf script
mode.

Suggested-by: Leo Yan <leo.yan@...aro.org>
Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
index 3e1a05bc82cc..5084bd2ca6eb 100644
--- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
+++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
@@ -324,8 +324,11 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
 		 * underflow.
 		 */
 		packet_queue->cs_timestamp = 0;
-		WARN_ONCE(true, "Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR
-				". Decoding may be improved with --itrace=Z...\n", indx);
+		if (!cs_etm__etmq_is_timeless(etmq))
+			pr_warning_once("Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR
+					". Decoding may be improved by prepending 'Z' to your current --itrace arguments.\n",
+					indx);
+
 	} else if (packet_queue->instr_count > elem->timestamp) {
 		/*
 		 * Sanity check that the elem->timestamp - packet_queue->instr_count would not
-- 
2.28.0