[PATCH AUTOSEL 6.10 01/24] drm/mediatek: Set sensible cursor width/height values to fix crash

[Sasha Levin]

From: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>

[ Upstream commit 042b8711a0beafb2c3b888bebe3c300ab4c817fa ]

Hardware-speaking, there is no feature-reduced cursor specific
plane, so this driver reserves the last all Overlay plane as a
Cursor plane, but sets the maximum cursor width/height to the
maximum value that the full overlay plane can use.

While this could be ok, it raises issues with common userspace
using libdrm (especially Mutter, but other compositors too) which
will crash upon performing allocations and/or using said cursor
plane.

Reduce the maximum width/height for the cursor to 512x512 pixels,
value taken from IGT's maximum cursor size test, which succeeds.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Reviewed-by: Fei Shao <fshao at chromium.org>
Tested-by: Fei Shao <fshao at chromium.org>
Reviewed-by: Daniel Stone <daniels at collabora.com>
Reviewed-by: CK Hu <ck.hu at mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240718082410.204459-1-angelogioacchino.delregno@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu at kernel.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 56f409ad7f390..ab2bace792e46 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -539,8 +539,8 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	}
 
 	/* IGT will check if the cursor size is configured */
-	drm->mode_config.cursor_width = drm->mode_config.max_width;
-	drm->mode_config.cursor_height = drm->mode_config.max_height;
+	drm->mode_config.cursor_width = 512;
+	drm->mode_config.cursor_height = 512;
 
 	/* Use OVL device for all DMA memory allocations */
 	crtc = drm_crtc_from_index(drm, 0);
-- 
2.43.0