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

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Date:   Wed, 22 Dec 2021 12:28:52 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     Marijn Suijten <marijn.suijten@...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

Il 11/12/21 22:57, Marijn Suijten ha scritto:
> On 2021-12-12 00:49:09, Dmitry Baryshkov wrote:
>> On Sun, 12 Dec 2021 at 00:35, Marijn Suijten
>> <marijn.suijten@...ainline.org> wrote:
>>> [..]
>>> 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?
> 
> I prefer calling _dpu_encoder_phys_cmd_wait_for_idle directly and
> optionally adding our own error message.  IIRC DRM_ERROR prints source
> information such as the function this originated from, and that makes it
> impossible to distinguish between the wait_for_tx_complete callback or
> the invocation through dpu_encoder_phys_cmd_wait_for_commit_done anyway.
> 
> - Marijn
> 

I wouldn't be happy to find myself in a situation in which I get strange
display slowness without any print to help me; for this reason, I find
having the print in place useful for debugging of both perf and fault.

Cheers,
- Angelo