linux-kernel - Re: [PATCH v2] drm/msm/dpu: Filter modes based on adjusted mode clock

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Message-ID: <88f04334-8d73-4ced-9c46-e69c3e6cbc72@oss.qualcomm.com>
Date: Mon, 20 Oct 2025 16:15:18 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Rob Clark <robdclark@...il.com>, Dmitry Baryshkov <lumag@...nel.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>, 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: Filter modes based on adjusted mode clock

On 10/20/25 4:05 PM, neil.armstrong@...aro.org wrote:
> Hi,
> 
> On 5/7/25 03:38, Jessica Zhang wrote:
>> Filter out modes that have a clock rate greater than the max core clock
>> rate when adjusted for the perf clock factor
>>
>> This is especially important for chipsets such as QCS615 that have lower
>> limits for the MDP max core clock.
>>
>> Since the core CRTC clock is at least the mode clock (adjusted for the
>> perf clock factor) [1], the modes supported by the driver should be less
>> than the max core clock rate.
>>
>> [1] https://elixir.bootlin.com/linux/v6.12.4/source/drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c#L83
>>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> 
> This change breaks the T14s OLED display, no modes are reported on the eDP connector.
> msm_dpu ae01000.display-controller: [drm:update_display_info.part.0 [drm]] [CONNECTOR:41:eDP-1] Assigning EDID-1.4 digital sink color depth as 10 bpc.
> msm_dpu ae01000.display-controller: [drm:update_display_info.part.0 [drm]] [CONNECTOR:41:eDP-1] ELD monitor
> msm_dpu ae01000.display-controller: [drm:update_display_info.part.0 [drm]] [CONNECTOR:41:eDP-1] ELD size 20, SAD count 0
> [drm:drm_mode_object_put.part.0 [drm]] OBJ ID: 113 (1)
> msm_dpu ae01000.display-controller: [drm:drm_mode_prune_invalid [drm]] Rejected mode: "2880x1800": 120 652260 2880 2912 2920 2980 1800 1808 1816 1824 0x48 0x9 (CLOCK_HIGH)
> msm_dpu ae01000.display-controller: [drm:drm_mode_prune_invalid [drm]] Rejected mode: "2880x1800": 60 652260 2880 2888 2920 2980 1800 1808 1816 3648 0x40 0x9 (CLOCK_HIGH)
> 
> With this reverted on v6.18-rc, display works again.

https://lore.kernel.org/linux-arm-msm/20250923-modeclk-fix-v2-1-01fcd0b2465a@oss.qualcomm.com/

Konrad