linux-kernel - Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

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Message-ID: <CAAq5pW9o3itC0G16LnJO7KMAQ_XoqXUpB=cuJ_7e3-H11zKd5Q@mail.gmail.com>
Date: Wed, 26 Nov 2025 14:06:50 +0900
From: Evans Jahja <evansjahja13@...il.com>
To: "angelogioacchino.delregno@...labora.com" <angelogioacchino.delregno@...labora.com>
Cc: linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when
 probing mediatek-drm

Hi Angelo, I was able to isolate the problem further to the dts. After
bisecting the arch/arm64/boot/dts/mediatek/ and building the dts, it
seems like this is the first commit that introduced the issue on my
device.

commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Date:   Thu Jul 24 10:39:08 2025 +0200

    arm64: dts: mediatek: mt8183: Migrate to display controller OF graph

I am linking my full bisect log here:

https://bugzilla.kernel.org/attachment.cgi?id=308962&action=edit

Thank you,

Evans Jahja

On Wed, Nov 26, 2025 at 3:01 AM Evans Jahja <evansjahja13@...il.com> wrote:
>
> Hi,
>
> I have a Lenovo IdeaPad Duet Chromebook CT-X636F, detected as Mediatek
> krane sku176 board. (mt8183-kukui-krane)
>
> The display failed to initialize on the mainline kernel (linux
> 6.18-rc7). Using the same config, on stable (linux 6.17.9) the display
> works fine.
>
> config: https://bugzilla.kernel.org/show_bug.cgi?id=220803
>
> With the system on mainline kernel, I was able to check the serial
> console, the error on dmesg looks like this:
>
> [    6.513400] mediatek-drm mediatek-drm.18.auto: Building display
> pipeline for MMSYS 0
> [    6.514983] mediatek-drm mediatek-drm.18.auto: Display HW Pipeline
> built with 9 components.
> [    6.515009] mediatek-drm mediatek-drm.18.auto: Invalid display hw
> pipeline. Last component: 38 (ret=-2)
> [    6.524422] mediatek-drm mediatek-drm.18.auto: probe with driver
> mediatek-drm failed with error -22
>
> Temporarily modifying mtk_drm_drv.c by commenting calls to
> mtk_drm_of_ddp_path_build_one CRTC_EXT and CRTC_THIRD allows the
> display to function even on mainline. I was also able to add some
> logging and determine that building the HW pipeline for CRTC_MAIN
> works, but because building CRTC_EXT fails, the entire display would
> not initialize.
>
> I am on ArchLinuxARM, its prebuilt kernel was based on linux 6.17.8
> with distro-specific patches, also failed to init display. I have not
> checked why that failed, I am currently focusing on a clean upstream
> kernel.
>
> Please let me know how I can help. My apologies but I am rather new
> and may confuse terminologies. I will update as I learn more about the
> issue.
>
> Best regards,
>
> Evans Jahja