linux-kernel - Re: [PATCH v3 01/10] drm/msm/dsi: Remove useless math in DSC calculations

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Message-ID: <3f5cb79b-f745-8b7b-bacd-f9ea2988baea@linaro.org>
Date:   Sun, 9 Oct 2022 21:52:40 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Douglas Anderson <dianders@...omium.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/10] drm/msm/dsi: Remove useless math in DSC
 calculations

On 09/10/2022 21:48, Marijn Suijten wrote:
> Multiplying a value by 2 and adding 1 to it always results in a value
> that is uneven, and that 1 gets truncated immediately when performing
> integer division by 2 again.  There is no "rounding" possible here.
> 
> After that target_bpp_x16 is used to store a multiplication of
> bits_per_pixel by 16 which is only ever read to immediately be divided
> by 16 again, and is elided in much the same way.
> 
> Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data")
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

-- 
With best wishes
Dmitry