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From:   Mike Leach <mike.leach@linaro.org>
Date:   Wed, 1 Nov 2023 09:38:17 +0000
Message-ID: <CAJ9a7VgJAN_mPrFZ7vQLqp-GJRKrNfKirNiJYocS6ce7GfgPcw@mail.gmail.com>
Subject: Re: [PATCH] coresight: etm4x: Fix width of CCITMIN field
To:     James Clark <james.clark@arm.com>
Cc:     coresight@lists.linaro.org, suzuki.poulose@arm.com,
        anshuman.khandual@arm.com, stable@vger.kernel.org,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
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On Mon, 30 Oct 2023 at 10:29, James Clark <james.clark@arm.com> wrote:
>
> CCITMIN is a 12 bit field and doesn't fit in a u8, so extend it to u16.
> This probably wasn't an issue previously because values higher than 255
> never occurred.
>
> But since commit 0f55b43dedcd ("coresight: etm: Override TRCIDR3.CCITMIN
> on errata affected cpus"), a comparison with 256 was done to enable the
> errata, generating the following W=1 build error:
>
>   coresight-etm4x-core.c:1188:24: error: result of comparison of
>   constant 256 with expression of type 'u8' (aka 'unsigned char') is
>   always false [-Werror,-Wtautological-constant-out-of-range-compare]
>
>    if (drvdata->ccitmin == 256)
>
> Cc: stable@vger.kernel.org
> Fixes: 54ff892b76c6 ("coresight: etm4x: splitting struct etmv4_drvdata")
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 20e2e4cb7614..da17b6c49b0f 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -1036,7 +1036,7 @@ struct etmv4_drvdata {
>         u8                              ctxid_size;
>         u8                              vmid_size;
>         u8                              ccsize;
> -       u8                              ccitmin;
> +       u16                             ccitmin;
>         u8                              s_ex_level;
>         u8                              ns_ex_level;
>         u8                              q_support;
> --
> 2.34.1
>

Reviewed-by: Mike Leach <mike.leach@linaro.org>

-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK