linux-kernel - Re: [PATCH v2] drm/msm/dpu: Set vsync source irrespective of mdp top support

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Message-ID: <aUu4RyJyZROn-FzQ@SoMainline.org>
Date: Wed, 24 Dec 2025 11:00:23 +0100
From: Marijn Suijten <marijn.suijten@...ainline.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Teguh Sobirin <teguh@...ir.in>, 
	Rob Clark <robin.clark@....qualcomm.com>, Dmitry Baryshkov <lumag@...nel.org>, 
	Abhinav Kumar <abhinav.kumar@...ux.dev>, Jessica Zhang <jesszhan0024@...il.com>, 
	Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dpu: Set vsync source irrespective of mdp top
 support

On 2025-11-21 14:16:55, Dmitry Baryshkov wrote:
> On Fri, Nov 21, 2025 at 02:02:08PM +0800, Teguh Sobirin wrote:
> > Since DPU 5.x the vsync source TE setup is split between MDP TOP and
> > INTF blocks.  Currently all code to setup vsync_source is only exectued
> > if MDP TOP implements the setup_vsync_source() callback. However on
> > DPU >= 8.x this callback is not implemented, making DPU driver skip all
> > vsync setup. Move the INTF part out of this condition, letting DPU
> > driver to setup TE vsync selection on all new DPU devices.
> > 
> > Signed-off-by: Teguh Sobirin <teguh@...ir.in>
> > ---
> > Changes in v2:
> > - Corrected commit message suggested by Dmitry Baryshkov.
> > - Link to v1: https://lore.kernel.org/linux-arm-msm/TYUPR06MB6099CBBE5090DB12A2C187E3DDFDA@TYUPR06MB6099.apcprd06.prod.outlook.com/
> > ---
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 22 +++++++++------------
> >  1 file changed, 9 insertions(+), 13 deletions(-)
> 
> Fixes: e955a3f0d86e ("drm/msm/dpu: Implement tearcheck support on INTF block")

Back at that commit, setup_vsync_source was still always assigned:

https://github.com/torvalds/linux/blob/e955a3f0d86e4a789364af62495ac37546eb71c8/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_top.c#L260-L263

While that was technically a wrong assumption by me - I should've put this loop
outside the hw_mdptop check in case that ever happened, it got unassigned in
commit 2f69e5458447 ("drm/msm/dpu: skip watchdog timer programming through TOP
on >= SM8450").

Note that this patch is a severe regression on DPU <5 and doesn't set up the WD
timer on DPU [5, 8), but I'll comment in-line on the diff.

- Marijn