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

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

On Fri, 2025-10-24 at 17:27 -0300, Ariel D'Alessandro wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> 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.

Reviewed-by: CK Hu <ck.hu@mediatek.com>

> 
> Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_plane.c | 24 +-----------------------
>  1 file changed, 1 insertion(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_plane.c b/drivers/gpu/drm/mediatek/mtk_plane.c
> index 02349bd440017..788b52c1d10c5 100644
> --- a/drivers/gpu/drm/mediatek/mtk_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_plane.c
> @@ -21,9 +21,6 @@
> 
>  static const u64 modifiers[] = {
>         DRM_FORMAT_MOD_LINEAR,
> -       DRM_FORMAT_MOD_ARM_AFBC(AFBC_FORMAT_MOD_BLOCK_SIZE_32x8 |
> -                               AFBC_FORMAT_MOD_SPLIT |
> -                               AFBC_FORMAT_MOD_SPARSE),
>         DRM_FORMAT_MOD_INVALID,
>  };
> 
> @@ -71,26 +68,7 @@ static bool mtk_plane_format_mod_supported(struct drm_plane *plane,
>                                            uint32_t format,
>                                            uint64_t modifier)
>  {
> -       if (modifier == DRM_FORMAT_MOD_LINEAR)
> -               return true;
> -
> -       if (modifier != DRM_FORMAT_MOD_ARM_AFBC(
> -                               AFBC_FORMAT_MOD_BLOCK_SIZE_32x8 |
> -                               AFBC_FORMAT_MOD_SPLIT |
> -                               AFBC_FORMAT_MOD_SPARSE))
> -               return false;
> -
> -       if (format != DRM_FORMAT_XRGB8888 &&
> -           format != DRM_FORMAT_ARGB8888 &&
> -           format != DRM_FORMAT_BGRX8888 &&
> -           format != DRM_FORMAT_BGRA8888 &&
> -           format != DRM_FORMAT_ABGR8888 &&
> -           format != DRM_FORMAT_XBGR8888 &&
> -           format != DRM_FORMAT_RGB888 &&
> -           format != DRM_FORMAT_BGR888)
> -               return false;
> -
> -       return true;
> +       return modifier == DRM_FORMAT_MOD_LINEAR;
>  }
> 
>  static void mtk_plane_destroy_state(struct drm_plane *plane,