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

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Message-ID: <20251024202756.811425-1-ariel.dalessandro@collabora.com>
Date: Fri, 24 Oct 2025 17:27:56 -0300
From: Ariel D'Alessandro <ariel.dalessandro@...labora.com>
To: chunkuang.hu@...nel.org,
	p.zabel@...gutronix.de,
	airlied@...il.com,
	simona@...ll.ch,
	matthias.bgg@...il.com,
	angelogioacchino.delregno@...labora.com,
	greenjustin@...omium.org,
	sjoerd@...labora.com
Cc: dri-devel@...ts.freedesktop.org,
	linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kernel@...labora.com,
	Ariel D'Alessandro <ariel.dalessandro@...labora.com>
Subject: [PATCH] drm/mediatek: Disable AFBC support on Mediatek DRM driver

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@...labora.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,