vc4/hvs: Support fixed alpha correctly on 2712D0

2712D0 removed alpha_mode from control word 2 for choosing fixed alpha
and replaced it with the previously reserved value of 3 in alpha_mask.

Handle this to fix corrupt desktop when using X on 2712D0

Signed-off-by: Dom Cobley <[email protected]>

Author: popcornmix

drivers/gpu/drm/vc4/vc4_plane.c

@@ -1079,6 +1079,20 @@ static u32 vc4_hvs5_get_alpha_blend_mode(struct drm_plane_state *state)
 	}
 }
 
+static u32 vc4_hvs6_get_alpha_mask_mode(struct drm_plane_state *state)
+{
+	struct drm_device *dev = state->state->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+
+	WARN_ON_ONCE(vc4->gen != VC4_GEN_6);
+
+	if (vc4->step_d0 && (!state->fb->format->has_alpha ||
+	    state->pixel_blend_mode == DRM_MODE_BLEND_PIXEL_NONE))
+		return VC4_SET_FIELD(SCALER6_CTL0_ALPHA_MASK_FIXED,
+		       SCALER6_CTL0_ALPHA_MASK);
+	return VC4_SET_FIELD(SCALER6_CTL0_ALPHA_MASK_NONE, SCALER6_CTL0_ALPHA_MASK);
+}
+
 /* Writes out a full display list for an active plane to the plane's
  * private dlist state.
  */
@@ -1822,7 +1836,7 @@ static int vc6_plane_mode_set(struct drm_plane *plane,
 	vc4_dlist_write(vc4_state,
 			SCALER6_CTL0_VALID |
 			VC4_SET_FIELD(tiling, SCALER6_CTL0_ADDR_MODE) |
-			VC4_SET_FIELD(0, SCALER6_CTL0_ALPHA_MASK) |
+			vc4_hvs6_get_alpha_mask_mode(state) |
 			(vc4_state->is_unity ? SCALER6_CTL0_UNITY : 0) |
 			VC4_SET_FIELD(format->pixel_order_hvs5, SCALER6_CTL0_ORDERRGBA) |
 			VC4_SET_FIELD(scl1, SCALER6_CTL0_SCL1_MODE) |

drivers/gpu/drm/vc4/vc4_regs.h

@@ -1408,6 +1408,9 @@ enum hvs_pixel_format {
 #define SCALER6_CTL0_ADDR_MODE_UIF		4
 
 #define SCALER6_CTL0_ALPHA_MASK_MASK		VC4_MASK(19, 18)
+#define SCALER6_CTL0_ALPHA_MASK_NONE		0
+#define SCALER6_CTL0_ALPHA_MASK_FIXED		3
+
 #define SCALER6_CTL0_UNITY			BIT(15)
 #define SCALER6_CTL0_ORDERRGBA_MASK		VC4_MASK(14, 13)
 #define SCALER6_CTL0_SCL1_MODE_MASK		VC4_MASK(10, 8)