[PATCH v2 3/3] drm/amd/display: advertise PIXEL_NONE as blend mode for DCE generations

DCE can support PREMULTI and COVERAGE blend mode depending on its
generation, however current driver implementation either doesn't expose
more than primary and cursor plane, or doesn't program registers for any
blend mode other than PIXEL_NONE. To fix the missing-blend-mode-prop
warning according to current DCE plane caps, create blend mode property
with PIXEL_NONE only for primary planes, instead of the DRM default
PREMULTI.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Signed-off-by: Melissa Wen <[email protected]>
---
 .../drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c    | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
index a276f3730044..60ccf1f9fcd9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
@@ -1923,14 +1923,18 @@ int amdgpu_dm_plane_init(struct amdgpu_display_manager *dm,
 	if (res)
 		return res;
 
-	/* TODO: Check which blend modes are supported in DCE-generation
-	 * planes, i.e. DC_PLANE_TYPE_DCE_RGB/UNDERLAY and expose blend mode
-	 * property accordingly.
+	/* Blend mode support varies on DCE generations according to HW caps
+	 * and number of planes per CRTC. However, as current driver
+	 * implementation only creates one primary and one cursor plane per
+	 * CRTC for DCE (overlay is only created if
+	 * DC_PLANE_TYPE_DCN_UNIVERSAL), the primary plane blend mode ends up
+	 * being always PIXEL_NONE across DCE versions.
 	 */
-	if ((plane->type == DRM_PLANE_TYPE_OVERLAY ||
+	if (plane_cap && plane_cap->type != DC_PLANE_TYPE_DCN_UNIVERSAL) {
+		drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_PIXEL_NONE));
+	} else if ((plane->type == DRM_PLANE_TYPE_OVERLAY ||
 	     plane->type == DRM_PLANE_TYPE_PRIMARY) &&
 	    plane_cap &&
-	    plane_cap->type == DC_PLANE_TYPE_DCN_UNIVERSAL &&
 	    plane_cap->per_pixel_alpha) {
 		unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
 					  BIT(DRM_MODE_BLEND_PREMULTI) |
-- 
2.53.0