From 313f798f52a5e46b0e419d05f977d40aaeac4106 Mon Sep 17 00:00:00 2001 From: Qinyun Tan Date: Tue, 1 Sep 2026 16:32:31 +0800 Subject: [PATCH] drm/ast: create blend mode property on cursor plane Since commit 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed"), drm_mode_config_validate() warns when a plane exposes an alpha pixel format but not the "pixel blend mode" property. The ast cursor plane (ARGB4444, ARGB8888) trips this on driver load: [PLANE:37:plane-1] pixel format with alpha exposed but blend mode not setup WARNING: drivers/gpu/drm/drm_mode_config.c:872 at drm_mode_config_validate+0x48f/0x510 [drm] ... Call Trace: drm_dev_register+0x1ce/0x290 [drm] ast_pci_probe+0x19d/0x3f0 [ast] local_pci_probe+0x41/0x90 Per Thomas Zimmermann's review, the ASPEED documentation describes the hardware cursor as blending with straight (non-pre-multiplied) alpha, which corresponds to DRM_MODE_BLEND_COVERAGE. Expose a "pixel blend mode" property advertising only DRM_MODE_BLEND_COVERAGE to make the hardware semantics explicit and silence the warning. Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed") Suggested-by: Thomas Zimmermann Reviewed-by: Thomas Zimmermann Tested-by: Thomas Zimmermann Signed-off-by: Qinyun Tan Signed-off-by: Thomas Zimmermann Link: https://patch.msgid.link/20260901083234.1828755-2-qinyuntan@linux.alibaba.com --- drivers/gpu/drm/ast/ast_cursor.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/ast/ast_cursor.c b/drivers/gpu/drm/ast/ast_cursor.c index fd19c45f2abe..690d4cd1db5e 100644 --- a/drivers/gpu/drm/ast/ast_cursor.c +++ b/drivers/gpu/drm/ast/ast_cursor.c @@ -25,6 +25,7 @@ #include #include +#include #include #include #include @@ -355,6 +356,8 @@ int ast_cursor_plane_init(struct ast_device *ast) } drm_plane_helper_add(cursor_plane, &ast_cursor_plane_helper_funcs); drm_plane_enable_fb_damage_clips(cursor_plane); + drm_plane_create_blend_mode_property(cursor_plane, + BIT(DRM_MODE_BLEND_COVERAGE)); return 0; }