[PATCH v4 1/3] drm/atomic-state-helper: set pixel_blend_mode to prop default on reset

[Melissa Wen <mwen@igalia.com>]

In __drm_atomic_helper_plane_state_init(), pixel_blend_mode is always
reset to DRM_MODE_BLEND_PREMULTI. That was consistent while
drm_plane_create_blend_mode_property() required PREMULTI in the
supported modes, but it now falls back to COVERAGE or PIXEL_NONE when
the driver doesn't support PREMULTI. The hardcoded default may therefore
not be a blend mode the hardware can do, nor one the property
advertises.

Initialize pixel_blend_mode from the blend mode property default
instead, keeping DRM_MODE_BLEND_PREMULTI for planes without the
property.

Fixes: 9813e158d13d ("drm/drm_blend: allow blend mode property without PREMULTI")
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
---
 drivers/gpu/drm/drm_atomic_state_helper.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index d90d1d7c9cf9..a2ef272e9f27 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -278,7 +278,14 @@ void __drm_atomic_helper_plane_state_init(struct drm_plane_state *plane_state,
 	plane_state->rotation = DRM_MODE_ROTATE_0;
 
 	plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
+
 	plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+	if (plane->blend_mode_property) {
+		if (!drm_object_property_get_default_value(&plane->base,
+							   plane->blend_mode_property,
+							   &val))
+			plane_state->pixel_blend_mode = val;
+	}
 
 	if (plane->color_encoding_property) {
 		if (!drm_object_property_get_default_value(&plane->base,
-- 
2.53.0