drm: rcar-du: Fix r8a779a0 color issue

The rcar DU driver on r8a779a0 has a bug causing some specific colors
getting converted to transparent colors, which then (usually) show as
black pixels on the screen.

The reason seems to be that the driver sets PnMR_SPIM_ALP bit in
PnMR.SPIM field, which is an illegal setting on r8a779a0. The
PnMR_SPIM_EOR bit also illegal.

Add a new feature flag for this (lack of a) feature and make sure the
bits are zero on r8a779a0.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -506,7 +506,8 @@ static const struct rcar_du_device_info rcar_du_r8a7799x_info = {
 static const struct rcar_du_device_info rcar_du_r8a779a0_info = {
 	.gen = 3,
 	.features = RCAR_DU_FEATURE_CRTC_IRQ
-		  | RCAR_DU_FEATURE_VSP1_SOURCE,
+		  | RCAR_DU_FEATURE_VSP1_SOURCE
+		  | RCAR_DU_FEATURE_NO_BLENDING,
 	.channels_mask = BIT(1) | BIT(0),
 	.routes = {
 		/* R8A779A0 has two MIPI DSI outputs. */

drivers/gpu/drm/rcar-du/rcar_du_drv.h

@@ -31,6 +31,7 @@ struct rcar_du_device;
 #define RCAR_DU_FEATURE_VSP1_SOURCE	BIT(2)	/* Has inputs from VSP1 */
 #define RCAR_DU_FEATURE_INTERLACED	BIT(3)	/* HW supports interlaced */
 #define RCAR_DU_FEATURE_TVM_SYNC	BIT(4)	/* Has TV switch/sync modes */
+#define RCAR_DU_FEATURE_NO_BLENDING	BIT(5)	/* PnMR.SPIM does not have ALP nor EOR bits */
 
 #define RCAR_DU_QUIRK_ALIGN_128B	BIT(0)	/* Align pitches to 128 bytes */
 

drivers/gpu/drm/rcar-du/rcar_du_plane.c

@@ -506,8 +506,15 @@ static void rcar_du_plane_setup_format_gen3(struct rcar_du_group *rgrp,
 					    unsigned int index,
 					    const struct rcar_du_plane_state *state)
 {
-	rcar_du_plane_write(rgrp, index, PnMR,
-			    PnMR_SPIM_TP_OFF | state->format->pnmr);
+	struct rcar_du_device *rcdu = rgrp->dev;
+	u32 pnmr = state->format->pnmr | PnMR_SPIM_TP_OFF;
+
+	if (rcdu->info->features & RCAR_DU_FEATURE_NO_BLENDING) {
+		/* No blending. ALP and EOR are not supported. */
+		pnmr &= ~(PnMR_SPIM_ALP | PnMR_SPIM_EOR);
+	}
+
+	rcar_du_plane_write(rgrp, index, PnMR, pnmr);
 
 	rcar_du_plane_write(rgrp, index, PnDDCR4,
 			    state->format->edf | PnDDCR4_CODE);
@@ -521,7 +528,6 @@ static void rcar_du_plane_setup_format_gen3(struct rcar_du_group *rgrp,
 	 * register to 0 to avoid this.
 	 */
 
-	/* TODO: Check if alpha-blending should be disabled in PnMR. */
 	rcar_du_plane_write(rgrp, index, PnALPHAR, 0);
 }