[PATCH v2 1/4] drm/vc4: Set premultiplied for alpha formats

[Stefan Schake]

Alpha formats in DRM are assumed to be premultiplied, so we should be
setting the PREMULT bit in the plane configuration for HVS.

Changes from v1:
 - Use correct has_alpha

Signed-off-by: Stefan Schake <stschake at gmail.com>
---
 drivers/gpu/drm/vc4/vc4_plane.c | 3 ++-
 drivers/gpu/drm/vc4/vc4_regs.h  | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index c4c7af1..831e195 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -618,13 +618,14 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 					      SCALER_POS1_SCL_HEIGHT));
 	}
 
-	/* Position Word 2: Source Image Size, Alpha Mode */
+	/* Position Word 2: Source Image Size, Alpha */
 	vc4_state->pos2_offset = vc4_state->dlist_count;
 	vc4_dlist_write(vc4_state,
 			VC4_SET_FIELD(fb->format->has_alpha ?
 				      SCALER_POS2_ALPHA_MODE_PIPELINE :
 				      SCALER_POS2_ALPHA_MODE_FIXED,
 				      SCALER_POS2_ALPHA_MODE) |
+			(fb->format->has_alpha ? SCALER_POS2_ALPHA_PREMULT : 0) |
 			VC4_SET_FIELD(vc4_state->src_w[0], SCALER_POS2_WIDTH) |
 			VC4_SET_FIELD(vc4_state->src_h[0], SCALER_POS2_HEIGHT));
 
diff --git a/drivers/gpu/drm/vc4/vc4_regs.h b/drivers/gpu/drm/vc4/vc4_regs.h
index b9749cb..a141496 100644
--- a/drivers/gpu/drm/vc4/vc4_regs.h
+++ b/drivers/gpu/drm/vc4/vc4_regs.h
@@ -848,6 +848,7 @@ enum hvs_pixel_format {
 #define SCALER_POS2_ALPHA_MODE_FIXED		1
 #define SCALER_POS2_ALPHA_MODE_FIXED_NONZERO	2
 #define SCALER_POS2_ALPHA_MODE_FIXED_OVER_0x07	3
+#define SCALER_POS2_ALPHA_PREMULT		BIT(29)
 
 #define SCALER_POS2_HEIGHT_MASK			VC4_MASK(27, 16)
 #define SCALER_POS2_HEIGHT_SHIFT		16
-- 
2.7.4