linux-kernel - Re: [PATCH v2 2/2] drm/msm/dpu: Fix timeout issues on command mode panels

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Date:   Sun, 12 Dec 2021 00:49:09 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        robdclark@...il.com, sean@...rly.run, airlied@...ux.ie,
        daniel@...ll.ch, abhinavk@...eaurora.org,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        konrad.dybcio@...ainline.org, martin.botka@...ainline.org,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        paul.bouchara@...ainline.org
Subject: Re: [PATCH v2 2/2] drm/msm/dpu: Fix timeout issues on command mode panels

On Sun, 12 Dec 2021 at 00:35, Marijn Suijten
<marijn.suijten@...ainline.org> wrote:
>
> On 2021-12-09 18:02:40, AngeloGioacchino Del Regno wrote:
> > Il 02/10/21 00:33, Dmitry Baryshkov ha scritto:
> > > On 11/09/2021 19:39, AngeloGioacchino Del Regno wrote:
> > >> [..]
> > > I've compared this with the MDP5 driver, where we always wait for PP_DONE
> > > interrupt. Would it be enough to always wait for it (= always call
> > > dpu_encoder_phys_cmd_wait_for_tx_complete())?
> > >
> >
> > Jokes apart, yes it would make sense to do that, it's something that works
> > at least... but we should verify that such a thing doesn't break new platforms
> > (like sm8150 and newer).
>
> On sm6125 (keeping in mind that we're on llvmpipe, will bring up the GPU
> later) none of this hurts the display:
>
> - Without this patch, so only checking for wait_for_ctl_start;
> - With this patch, checking for idle if it was already started;
> - With this patch altered to only ever call wait_for_tx_complete (wait
>   for idle), in place of wait_for_ctl_start.
>
> Working in the sense that glxgears, which actually reports a framerate
> of approx 170 despite being on llvmpipe on an SoC that is still in
> snail-mode, seems to update (commit) the panel smoothly on every
> occasion.
>
> On this note, does it perhaps make more sense to call the "internal"
> _dpu_encoder_phys_cmd_wait_for_idle function directly, instead of going
> through the "public" dpu_encoder_phys_cmd_wait_for_tx_complete which
> seems solely intended to handle the wait_for_tx_complete callback?

Either one would work. The main difference is the error message. Do
you want to see it here if the wait times out or not?

-- 
With best wishes
Dmitry