linux-kernel - Re: [Freedreno] [PATCH v3 06/10] drm/msm/dsi: Migrate to drm_dsc_compute_rc

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Message-ID: <20221017085944.2r24uqg73irmziqm@SoMainline.org>
Date:   Mon, 17 Oct 2022 10:59:44 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     phone-devel@...r.kernel.org, Vinod Koul <vkoul@...nel.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        David Airlie <airlied@...il.com>,
        linux-arm-msm@...r.kernel.org,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        dri-devel@...ts.freedesktop.org,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Martin Botka <martin.botka@...ainline.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Daniel Vetter <daniel@...ll.ch>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        freedreno@...ts.freedesktop.org, Sean Paul <sean@...rly.run>,
        linux-kernel@...r.kernel.org, Newbyte <newbie13xd@...il.com>,
        Caleb Connolly <caleb@...nolly.tech>
Subject: Re: [Freedreno] [PATCH v3 06/10] drm/msm/dsi: Migrate to
 drm_dsc_compute_rc_parameters()

On 2022-10-13 09:02:44, Abhinav Kumar wrote:
> On 10/13/2022 2:36 AM, Marijn Suijten wrote:
> > On 2022-10-12 16:03:06, Abhinav Kumar wrote:
> >> [..]
> >> But I would like to hold back this change till Vinod clarifies because
> >> Vinod had mentioned that with drm_dsc_compute_rc_parameters() he was
> >> seeing a mismatch in the computation of two values.
> >>
> >> slice_bpg_offset and the final_offset.
> > 
> > Unsurprisingly so because final_offset, and slice_bpg_offset through
> > initial_offset depend directly on bits_per_pixel.  The main takeaway of
> > this series is that Vinod was interpreting this field as integer instead
> > of containing 4 fractional bits.  If he updates his the panel driver [1]
> > to set bits_per_pixel = 8 << 4 instead of just 8 to account for this,
> > the values should check out once again.
> > 
> > [1]: https://git.linaro.org/people/vinod.koul/kernel.git/commit/?h=topic/pixel3_5.18-rc1&id=1d7d98ad564f1ec69e7525e07418918d90f247a1
> > 
> > Once Vinod (or someone else in the posession of a Pixel 3) confirms
> > this, I can respin this series and more explicitly explain why the FIXME
> > was put in place, instead of being resolved outright?
> > 
> > - Marijn
> 
> Makes perfect sense to me.
> 
> Will just wait for Vinod's tested-by.

Unfortunately Vinod doesn't have access to this device anymore, but
Caleb recently sent the support series including display driver for
Pixel 3 and is picking up the testing.  User "Newbyte" from #linux-msm
promised to test on the LG G7 to have even more input samples.

- Marijn