linux-kernel - Re: [PATCH 2/6] perf cs-etm: Initialise architecture based on TRCIDR1

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Message-ID: <20210731060312.GB7437@leoy-ThinkPad-X240s>
Date:   Sat, 31 Jul 2021 14:03:12 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     James Clark <james.clark@....com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Coresight ML <coresight@...ts.linaro.org>,
        Al Grant <al.grant@....com>,
        "Suzuki K. Poulose" <suzuki.poulose@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 2/6] perf cs-etm: Initialise architecture based on TRCIDR1

On Thu, Jul 22, 2021 at 12:10:35PM +0100, Mike Leach wrote:
> HI James
> 
> On Wed, 21 Jul 2021 at 10:07, James Clark <james.clark@....com> wrote:
> >
> > Currently the architecture is hard coded as ARCH_V8, but with the
> > introduction of ETE we want to pick ARCH_AA64. And this change is also
> > applicable to ETM v4.4 onwards as well.
> >
> > Signed-off-by: James Clark <james.clark@....com>
> > ---
> >  tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > 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 30889a9d0165..5972a8afcc6b 100644
> > --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > @@ -126,6 +126,18 @@ static int cs_etm_decoder__gen_etmv3_config(struct cs_etm_trace_params *params,
> >         return 0;
> >  }
> >
> > +#define TRCIDR1_TRCARCHMIN_SHIFT 4
> > +#define TRCIDR1_TRCARCHMIN_MASK  GENMASK(7, 4)
> > +#define TRCIDR1_TRCARCHMIN(x)    (((x) & TRCIDR1_TRCARCHMIN_MASK) >> TRCIDR1_TRCARCHMIN_SHIFT)
> > +static enum _ocsd_arch_version cs_etm_decoder__get_arch_ver(u32 reg_idr1)
> > +{
> > +       /*
> > +        * If the ETM trace minor version is 4 or more then we can assume
> > +        * the architecture is ARCH_AA64 rather than just V8
> > +        */
> > +       return TRCIDR1_TRCARCHMIN(reg_idr1) >= 4 ? ARCH_AA64 : ARCH_V8;
> > +}
> 
> This is true for ETM4.x & ETE 1.x (arch 5.x) but not ETM 3.x
> Probably need to beef up this comment or the function name to emphasise this.

Yeah, I think it's good to change the function name.  Eventually, this
function should only be used for ETM4.x and ETE.

Another minor comment is: can we refine the arch version number, e.g.
change the OpenCSD's macro "ARCH_AA64" to "ARCH_V8R4", (or
"ARCH_V8R3_AA64"), this can give more clear clue what's the ETM version.

And a nitpick: how about to change OpenCSD macro "ARCH_V8r3" to
"ARCH_V8R3" and assign it for ETMv4.3 IPs.

Thanks,
Leo