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

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Message-ID: <5scqahnsr5i26rkumg5eqdiwrg5n7rrnrp5642c6moxucf6w3r@xcgrxtjhj3pz>
Date: Thu, 10 Oct 2024 18:20:36 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
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 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)?

> [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