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

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Message-ID: <b325fc8d-e06b-36de-b40a-b5ffbcebb1c5@linaro.org>
Date:   Sat, 2 Oct 2021 01:33:28 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>, robdclark@...il.com
Cc:     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,
        marijn.suijten@...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 11/09/2021 19:39, 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).

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())?

> 
> 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..aa5d3b3cef15 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(phys_enc->hw_ctl))
> +		return dpu_encoder_phys_cmd_wait_for_tx_complete(phys_enc);
> +
>   	return _dpu_encoder_phys_cmd_wait_for_ctl_start(phys_enc);
>   }
>   
> 


-- 
With best wishes
Dmitry