linux-kernel - Re: [PATCH 2/2] drm/msm/dpu: try reserving the DSPP-less LM first

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Message-ID: <ci7m26yyzojptbfzengfhuudhqbofmljkxbraufpsnlvnzl7us@35hmb6vjabjp>
Date: Tue, 27 Jan 2026 13:18:03 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Val Packett <val@...kett.cool>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/msm/dpu: try reserving the DSPP-less LM first

On Tue, Jan 27, 2026 at 07:59:34AM -0300, Val Packett wrote:
> 
> On 1/27/26 7:34 AM, Dmitry Baryshkov wrote:
> > On Tue, Jan 27, 2026 at 06:43:32AM -0300, Val Packett wrote:
> > > this has massively broken things on my x1e device (latitude-7455):
> > > [..]
> > > Reverted only this commit and it's back to normal, so I'm pretty sure it's
> > > this.
> > Interesting. Could you please capture the dri-state (only the last part,
> > resource mapping) with the external monitor attached and with this
> > commit reverted?
> 
> Just reverted:
> 
> crtc[106]: crtc-0 [..]
>         mode: "2560x1600": 60 280710 2560 2608 2640 2720 1600 1603 1609 1720
> 0x48 0x9
>         lm[0]=0
>         ctl[0]=0
>         dspp[0]=0
>         lm[1]=1
>         ctl[1]=0
>         dspp[1]=1
> crtc[107]: crtc-1 [..]
>         mode: "3840x2560": 60 631750 3840 3888 3920 4000 2560 2563 2573 2633
> 0x48 0x9
>         lm[0]=2
>         ctl[0]=1
>         lm[1]=3
>         ctl[1]=1
> resource mapping: pingpong=106 106 107 107 # # - - # # - - - mixer=106 106
> 107 107 # # - - ctl=106 107 # # # # - - dspp=# # # # - - - - dsc=# # # # - -
> - - cdm=# sspp=# # # # - - - - # # # # # # - - cwb=- - - -
> 
> > Also, could you please run another check:
> >   - revert this commit
> >   - comment out LM_2, LM_3 in the catalog
> >   - try the resulting kernel with the external monitor
> 
> Commented out:

Thanks! I assume external monitor is working fine?

> 
> crtc[106]: crtc-0 [..]
>         mode: "2560x1600": 60 280710 2560 2608 2640 2720 1600 1603 1609 1720
> 0x48 0x9
>         lm[0]=0
>         ctl[0]=0
>         dspp[0]=0
>         lm[1]=1
>         ctl[1]=0
>         dspp[1]=1
> crtc[107]: crtc-1 [..]
>         mode: "3840x2560": 60 631750 3840 3888 3920 4000 2560 2563 2573 2633
> 0x48 0x9
>         lm[0]=4
>         ctl[0]=1
>         lm[1]=5
>         ctl[1]=1
> resource mapping:
>         pingpong=106 106 # # 107 107 - - # # - - -
>         mixer=106 106 - - 107 107 - -
>         ctl=106 107 # # # # - -
>         dspp=# # # # - - - -
>         dsc=# # # # - - - -
>         cdm=#
>         sspp=# # # # - - - - # # # # # # - -
>         cwb=- - - -
> 
> Not sure why the dspp= line in resource mapping doesn't show any numbers
> when a crtc has dspp[0]= and dspp[1]= o.0

Ah, it might be confusing. The crtc-N blocks shows that LM in theory has
DSPP blocks.

Resource mapping shows if the DSPP is actually allocated (aka used for
the post processing).

> 
> But with LM 4+5, gamma control doesn't affect the external monitor.

Yes, that's expected.

> 
> 
> ~val
> 

-- 
With best wishes
Dmitry