linux-kernel - Re: [PATCH] coresight: etm4x: Fix width of CCITMIN field

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Date:   Thu, 2 Nov 2023 09:44:30 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        suzuki.poulose@....com
Cc:     stable@...r.kernel.org, Mike Leach <mike.leach@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: etm4x: Fix width of CCITMIN field



On 10/30/23 15:59, James Clark 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@...r.kernel.org
> Fixes: 54ff892b76c6 ("coresight: etm4x: splitting struct etmv4_drvdata")
> Signed-off-by: James Clark <james.clark@....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;

Thanks James, so this takes care of the Smatch static checker
warning as reported by Dan Carpenter earlier.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>