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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 27 Apr 2022 17:59:16 +0200
Message-ID: <CAK8P3a3_Ea2Szn61D-t--52V-zk+B-sq2mi5YbfMbTim7M9ZAQ@mail.gmail.com>
Subject: Re: [PATCHv10 4/6] drm/meson: Fix overflow implicit truncation warnings
To:     Sai Prakash Ranjan <quic_saipraka@quicinc.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Marc Zyngier <maz@kernel.org>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        quic_psodagud@quicinc.com, gregkh <gregkh@linuxfoundation.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        kernel test robot <lkp@intel.com>
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On Thu, Feb 24, 2022 at 7:07 AM Sai Prakash Ranjan
<quic_saipraka@quicinc.com> wrote:
>
> Fix -Woverflow warnings for drm/meson driver which is a result
> of moving arm64 custom MMIO accessor macros to asm-generic function
> implementations giving a bonus type-checking now and uncovering these
> overflow warnings.
>
> drivers/gpu/drm/meson/meson_viu.c: In function ‘meson_viu_init’:
> drivers/gpu/drm/meson/meson_registers.h:1826:48: error: large integer implicitly truncated to unsigned type [-Werror=overflow]
>  #define  VIU_OSD_BLEND_REORDER(dest, src)      ((src) << (dest * 4))
>                                                 ^
> drivers/gpu/drm/meson/meson_viu.c:472:18: note: in expansion of macro ‘VIU_OSD_BLEND_REORDER’
>    writel_relaxed(VIU_OSD_BLEND_REORDER(0, 1) |
>                   ^~~~~~~~~~~~~~~~~~~~~
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Neil Armstrong <narmstrong@baylibre.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

It took me a bit to understand why we got the warning in the first place, but I
should have just read the patch description, it's all there....