linux-kernel - Re: [PATCH] drm/msm/dpu: Don't always set merge

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Message-ID: <9cfae7b6-f05e-4db6-ac86-9236e786fbf4@quicinc.com>
Date: Mon, 14 Oct 2024 13:30:04 -0700
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "Marijn
 Suijten" <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        <quic_abhinavk@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, Rob Clark
	<robdclark@...omium.org>
Subject: Re: [PATCH] drm/msm/dpu: Don't always set merge_3d pending flush



On 10/10/2024 8:20 AM, Dmitry Baryshkov wrote:
> On Wed, Oct 09, 2024 at 08:41:13PM GMT, Jessica Zhang wrote:
>> Don't set the merge_3d pending flush bits if the mode_3d is
>> BLEND_3D_NONE.
>>
>> Always flushing merge_3d can cause timeout issues when there are
>> multiple commits with concurrent writeback enabled.
>>
>> This is because the video phys enc waits for the hw_ctl flush register
>> to be completely cleared [1] in its wait_for_commit_done(), but the WB
>> encoder always sets the merge_3d pending flush during each commit
>> regardless of if the merge_3d is actually active.
>>
>> This means that the hw_ctl flush register will never be 0 when there are
>> multiple CWB commits and the video phys enc will hit vblank timeout
>> errors after the first CWB commit.
> 
>  From this description, wouldn't it be more correct to always set
> intf_cfg.merge_3d in WB code (even if mode_3d is NONE)?

Hi Dmitry,

This discussion should be addressed in [1].

Thanks,

Jessica Zhang

[1] https://patchwork.freedesktop.org/series/139824/

> 
>> [1] commit fe9df3f50c39 ("drm/msm/dpu: add real wait_for_commit_done()")
>>
>> Fixes: 3e79527a33a8 ("drm/msm/dpu: enable merge_3d support on sm8150/sm8250")
>> Fixes: d7d0e73f7de3 ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 5 ++++-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c  | 5 ++++-
>>   2 files changed, 8 insertions(+), 2 deletions(-)
>>
> 
> -- 
> With best wishes
> Dmitry