Hi, Justin:

AFBC just improve DRAM bandwidth performance, so I decide to backport this disable patch. Once fixup patch exist, then backport fixup patch.

Regards, CK

On Tue, 2025-10-28 at 10:48 +0000, Macpaul Lin (林智斌) wrote:

On Fri, 2025-10-24 at 17:27 -0300, Ariel D'Alessandro wrote:

...

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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.

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,

Great! Thanks for this patch. I've tested this patch against k6.17.5 on mt8395-genio-1200-evk board, and it is working. I've also tested this patch with 'modetest -M mediatek -s 34@59:1200x1290' is working as well.

I'm not sure if it is possible to add a "Fixes:" tag to this patch? Maybe add this patch with 'Cc: stable@vger.kernel.org #6.17' at least? Some Linux distros are currently using 6.17 for testing.

Reviewed-by: Macpaul Lin macpaul.lin@mediatek.com

Regards, Macpaul Lin

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