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Message-ID: <ca33cb5d-363d-dddd-4ad9-62f8a2d87bb1@linaro.org>
Date:   Wed, 14 Dec 2022 20:52:54 +0200
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Subject: Re: [RFC PATCH 4/6] drm/msm/dsi: Use DSC slice(s) packet size to
 compute word count
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To:     Marijn Suijten <marijn.suijten@somainline.org>,
        phone-devel@vger.kernel.org, Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Vinod Koul <vkoul@kernel.org>
Cc:     ~postmarketos/upstreaming@lists.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@somainline.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Martin Botka <martin.botka@somainline.org>,
        Jami Kettunen <jami.kettunen@somainline.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Stephen Boyd <swboyd@chromium.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Jessica Zhang <quic_jesszhan@quicinc.com>,
        =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>,
        Kuogee Hsieh <quic_khsieh@quicinc.com>,
        Jani Nikula <jani.nikula@intel.com>,
        sunliming <sunliming@kylinos.cn>,
        Sam Ravnborg <sam@ravnborg.org>,
        Haowen Bai <baihaowen@meizu.com>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Loic Poulain <loic.poulain@linaro.org>,
        Vinod Polimera <quic_vpolimer@quicinc.com>,
        Douglas Anderson <dianders@chromium.org>,
        Vladimir Lypak <vladimir.lypak@gmail.com>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20221213232207.113607-1-marijn.suijten@somainline.org>
 <20221213232207.113607-5-marijn.suijten@somainline.org>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <20221213232207.113607-5-marijn.suijten@somainline.org>
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On 14/12/2022 01:22, Marijn Suijten wrote:
> According to downstream the value to use for WORD_COUNT is
> bytes_per_pkt, which denotes the number of bytes in a packet based on
> how many slices have been configured by the panel driver times the
> width of a slice times the number of bytes per pixel.
> 
> The DSC panels seen thus far use one byte per pixel, only one slice
> per packet, and a slice width of half the panel width leading to the
> desired bytes_per_pkt+1 value to be equal to hdisplay/2+1.  This however
> isn't the case anymore for panels that configure two slices per packet,
> where the value should now be hdisplay+1.
> 
> Note that the aforementioned panel (on a Sony Xperia XZ3, sdm845) with
> slice_count=1 has also been tested to successfully accept slice_count=2,
> which would have shown corrupted output previously.
> 
> Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")
> Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

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

-- 
With best wishes
Dmitry