linux-kernel - Re: [PATCH v3 1/3] drm/msm/dpu: check mode against PINGPONG or DSC max width

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Message-ID: <CAO9ioeXY=rzZkJi=Lz4-JDASSnE7DWBh59aPawrPSzrFFPCNbw@mail.gmail.com>
Date: Mon, 12 Jan 2026 09:31:07 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Xilin Wu <sophon@...xa.com>
Cc: 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>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        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,
        Jessica Zhang <jessica.zhang@....qualcomm.com>
Subject: Re: [PATCH v3 1/3] drm/msm/dpu: check mode against PINGPONG or DSC
 max width

On Mon, 12 Jan 2026 at 09:25, Xilin Wu <sophon@...xa.com> wrote:
>
> On 1/12/2026 11:11 AM, Dmitry Baryshkov wrote:
> > From: Jessica Zhang <jessica.zhang@....qualcomm.com>
> >
> > LM block doesn't have a hardware buffer (unlike PINGPONG and DSC
> > encoders). As such, don't use ephemeral max_mixer_width and
> > MAX_HDISPLAY_SPLIT to validate requested modes. Instead use PP and DSC
> > buffer widths.
> >
> > While on the DPU 8.x+ supports a max linewidth of 8960 for PINGPONG_0,
> > there is some additional logic that needs to be added to the resource
> > manager to specifically try and reserve PINGPONG_0 for modes that are
> > greater than 5k.
> >
> > Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> > Tested-by: Xilin Wu <sophon@...xa.com> # qcs6490-radxa-dragon-q6a
> > [DB: reworked to drop catalog changes, updated commit message]
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>
> Sorry for the late reply, my colleagues are still testing the new series
> on qcs6490.
>
> However, this completely breaks 4K 120Hz display on SC8280XP CRD, which
> was previously functional (albeit with the clock check bypassed [1]).
> The display now shows a solid blue screen. Kernel logs indicate that
> only one layer mixer is being used, instead of the two that were used
> previously.

Interesting, thanks.

>
> [1]
> https://lore.kernel.org/all/F4CDF36128041430+0d030e3b-054c-4910-a132-72273c541948@radxa.com/
>
> --
> Best regards,
> Xilin Wu <sophon@...xa.com>



-- 
With best wishes
Dmitry