linux-kernel - Re: [PATCH v2 5/7] drm/msm/dsi: Account for DSC's bits_per

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Date:   Wed, 5 Oct 2022 23:33:39 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        ~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>,
        Daniel Vetter <daniel@...ll.ch>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Douglas Anderson <dianders@...omium.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH v2 5/7] drm/msm/dsi: Account for DSC's bits_per_pixel
 having 4 fractional bits

On 2022-10-06 00:11:06, Dmitry Baryshkov wrote:
> On 06/10/2022 00:08, Marijn Suijten wrote:
> > [..]
> > Aside fixing that to assign these values (through the proper constants)
> > to dsc->mux_word_size, is it worth looking for the right parameters for
> > other bpc or return -EINVAL if bpc isn't 8, to uphold this comment until
> > support for other bpc is validated?
> 
> I'd say, return -EINVAL or -EOPNOTSUPP for now, let's fix that later. 
> It's definitely a separate change. Let's wait for a device with such 
> panel to be able to test it.

According to [1] these four fields specifically are different for other
BPC; I can add a -EOPNOTSUPP and DRM_DEV_ERROR requesting a test, or
insert the values; there's only 8BPC and 10BPC, no 12BPC.

Aside that we need a different initial_offset = 5632 for other bpp/bpc
pairs.

[1]: https://git.codelinaro.org/clo/la/platform/vendor/opensource/display-drivers/-/blob/DISPLAY.LA.2.0.r1-08000-WAIPIO.0/msm/sde_dsc_helper.c#L110-139

- Marijn