drm/vc4: plane: Expand the lower bits by repeating the higher bits

mripard · anholt · commit 3257ec797d3a · 2018-05-17T15:22:43.000+01:00
The vc4 HVS uses an internal RGB888 representation of the frames, and will by default expand formats using a lower depth using zeros. This causes an issue when we try to use other compositing software such as pixman that fill the missing bits by repeating the higher significant bits. As such, we can't check the display output in a reliable way by doing a software composition and an hardware one and compare both. To prevent this, force the same behaviour so that we can do such things. Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com> Signed-off-by: Eric Anholt <eric@anholt.net> Link: https://patchwork.freedesktop.org/patch/msgid/20180517133759.25626-1-maxime.ripard@bootlin.com
diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -544,6 +544,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
 	/* Control word */
 	vc4_dlist_write(vc4_state,
 			SCALER_CTL0_VALID |
+			VC4_SET_FIELD(SCALER_CTL0_RGBA_EXPAND_ROUND, SCALER_CTL0_RGBA_EXPAND) |
 			(format->pixel_order << SCALER_CTL0_ORDER_SHIFT) |
 			(format->hvs << SCALER_CTL0_PIXEL_FORMAT_SHIFT) |
 			VC4_SET_FIELD(tiling, SCALER_CTL0_TILING) |
