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

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Date:   Fri, 10 Sep 2021 23:48:20 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
Cc:     robdclark@...il.com, sean@...rly.run, airlied@...ux.ie,
        daniel@...ll.ch, dmitry.baryshkov@...aro.org,
        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 2/2] drm/msm/dpu: Fix timeout issues on command mode
 panels

Hi Angelo!

On 2021-09-01 19:43:47, AngeloGioacchino Del Regno wrote:
> In function dpu_encoder_phys_cmd_wait_for_commit_done we are always
> checking if the relative CTL is started by waiting for an interrupt
> to fire: it is fine to do that, but then sometimes we call this
> function while the CTL is up and has never been put down, but that
> interrupt gets raised only when the CTL gets a state change from
> 0 to 1 (disabled to enabled), so we're going to wait for something
> that will never happen on its own.
> 
> Solving this while avoiding to restart the CTL is actually possible
> and can be done by just checking if it is already up and running
> when the wait_for_commit_done function is called: in this case, so,
> if the CTL was already running, we can say that the commit is done
> if the command transmission is complete (in other terms, if the
> interface has been flushed).
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
> index aa01698d6b25..b5b1b555ac4e 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
> @@ -682,6 +682,9 @@ static int dpu_encoder_phys_cmd_wait_for_commit_done(
>  	if (!dpu_encoder_phys_cmd_is_master(phys_enc))
>  		return 0;
>  
> +	if (phys_enc->hw_ctl->ops.is_started)
> +		return dpu_encoder_phys_cmd_wait_for_tx_complete(phys_enc);

In the previous commit you introduced is_started to the ops struct as
function pointer, and you probably intend to call it here instead of
just checking whether it might be NULL.

As far as I remember this was also the reason for previously mentioning
that it was faulty and required a v2 in:
https://lore.kernel.org/linux-arm-msm/bdc67afc-3736-5497-c43f-5165c55e0354@somainline.org/

Thanks!

- Marijn

> +
>  	return _dpu_encoder_phys_cmd_wait_for_ctl_start(phys_enc);
>  }
>  
> -- 
> 2.32.0
>