linux-kernel - Re: [PATCH] perf cs-etm: Improve version detection and error reporting

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Message-ID: <20240430195124.GD125@debian-dev>
Date: Wed, 1 May 2024 03:51:24 +0800
From: Leo Yan <leo.yan@...ux.dev>
To: James Clark <james.clark@....com>
Cc: linux-perf-users@...r.kernel.org, coresight@...ts.linaro.org,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
	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>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf cs-etm: Improve version detection and error
 reporting

On Tue, Apr 30, 2024 at 02:32:21PM +0100, James Clark wrote:
> When the config validation functions are warning about ETMv3, they do it
> based on "not ETMv4". If the drivers aren't all loaded or the hardware
> doesn't support Coresight it will appear as "not ETMv4" and then Perf
> will print the error message "... not supported in ETMv3 ..." which is
> wrong and confusing.
> 
> cs_etm_is_etmv4() is also misnamed because it also returns true for
> ETE because ETE has a superset of the ETMv4 metadata files. Although
> this was always done in the correct order so it wasn't a bug.
> 
> Improve all this by making a single get version function which also
> handles not present as a separate case. Change the ETMv3 error message
> to only print when ETMv3 is detected, and add a new error message for
> the not present case.
> 
> Signed-off-by: James Clark <james.clark@....com>

Reviewed-by: Leo Yan <leo.yan@...ux.dev>