[PATCH] drm/mediatek: Disable AFBC support on Mediatek DRM driver

[Chun-Kuang Hu]

Ariel D'Alessandro <ariel.dalessandro at collabora.com> 於 2025年10月24日 週五 下午8:28寫道：
>
> Commit c410fa9b07c32 ("drm/mediatek: Add AFBC support to Mediatek DRM
> driver") added AFBC support to Mediatek DRM and enabled the
> 32x8/split/sparse modifier.
>
> However, this is currently broken on Mediatek MT8188 (Genio 700 EVK
> platform); tested using upstream Kernel and Mesa (v25.2.1), AFBC is used by
> default since Mesa v25.0.
>
> Kernel trace reports vblank timeouts constantly, and the render is garbled:
>
> ```
> [CRTC:62:crtc-0] vblank wait timed out
> WARNING: CPU: 7 PID: 70 at drivers/gpu/drm/drm_atomic_helper.c:1835 drm_atomic_helper_wait_for_vblanks.part.0+0x24c/0x27c
> [...]
> Hardware name: MediaTek Genio-700 EVK (DT)
> Workqueue: events_unbound commit_work
> pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : drm_atomic_helper_wait_for_vblanks.part.0+0x24c/0x27c
> lr : drm_atomic_helper_wait_for_vblanks.part.0+0x24c/0x27c
> sp : ffff80008337bca0
> x29: ffff80008337bcd0 x28: 0000000000000061 x27: 0000000000000000
> x26: 0000000000000001 x25: 0000000000000000 x24: ffff0000c9dcc000
> x23: 0000000000000001 x22: 0000000000000000 x21: ffff0000c66f2f80
> x20: ffff0000c0d7d880 x19: 0000000000000000 x18: 000000000000000a
> x17: 000000040044ffff x16: 005000f2b5503510 x15: 0000000000000000
> x14: 0000000000000000 x13: 74756f2064656d69 x12: 742074696177206b
> x11: 0000000000000058 x10: 0000000000000018 x9 : ffff800082396a70
> x8 : 0000000000057fa8 x7 : 0000000000000cce x6 : ffff8000823eea70
> x5 : ffff0001fef5f408 x4 : ffff80017ccee000 x3 : ffff0000c12cb480
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c12cb480
> Call trace:
>  drm_atomic_helper_wait_for_vblanks.part.0+0x24c/0x27c (P)
>  drm_atomic_helper_commit_tail_rpm+0x64/0x80
>  commit_tail+0xa4/0x1a4
>  commit_work+0x14/0x20
>  process_one_work+0x150/0x290
>  worker_thread+0x2d0/0x3ec
>  kthread+0x12c/0x210
>  ret_from_fork+0x10/0x20
> ---[ end trace 0000000000000000 ]---
> ```
>
> Until this gets fixed upstream, disable AFBC support on this platform, as
> it's currently broken with upstream Mesa.

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-fixes

Regards,
Chun-Kuang.

>
> Signed-off-by: Ariel D'Alessandro <ariel.dalessandro at collabora.com>
> ---