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

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Date:   Mon, 17 Oct 2022 13:37:11 +0000
From:   Caleb Connolly <caleb@...nolly.tech>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        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>
Subject: Re: [Freedreno] [PATCH v3 06/10] drm/msm/dsi: Migrate to drm_dsc_compute_rc_parameters()



On 17/10/2022 09:59, Marijn Suijten wrote:
> 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.

Hi,

I'm hoping to pick the Pixel 3 stuff back up at some point, but right now there
seem to be quite a few issues outside of DSC which make testing it a bit of a pain.

I gave Marijn's series [1] a go but wasn't able to get anything usable out of the
panel, however I doubt this is a DSC issue as I've always needed some hacks to
get the panel working - I've never had any success with it without skipping both
the initial panel reset and sending the PPS payload.

I think if Marijn has managed to initialise a panel properly then the lack of
Pixel 3 for validation shouldn't be a blocker to merge these fixes.

[1]:
https://lore.kernel.org/linux-arm-msm/20221009184824.457416-1-marijn.suijten@somainline.org/

>
> - Marijn

--
Kind Regards,
Caleb