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

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Message-ID: <CAAq5pW_saBZ+52zz2FYTt9SuWXj2KwX2Ld7AggVKAzca2m0Oow@mail.gmail.com>
Date: Wed, 26 Nov 2025 03:01:21 +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: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when
 probing mediatek-drm

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