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

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Message-ID: <20211211213528.uroqfdksvokspbxf@SoMainline.org>
Date:   Sat, 11 Dec 2021 22:35:28 +0100
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
Cc:     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 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?

- Marijn