diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
index 9a9bc8bcda3051344784620894e39f8656e1feed..501d79367e3efce6544e9f14810ddabaa393472b 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
@@ -512,6 +512,18 @@ static void rcar_du_plane_setup_format_gen3(struct rcar_du_group *rgrp,
 
 	rcar_du_plane_write(rgrp, index, PnDDCR4,
 			    state->format->edf | PnDDCR4_CODE);
+
+	/*
+	 * On Gen3, some DU channels have two planes, each being wired to a
+	 * separate VSPD instance. The DU can then blend two planes. While
+	 * this feature isn't used by the driver, issues related to alpha
+	 * blending (such as incorrect colors or planes being invisible) may
+	 * still occur if the PnALPHAR register has a stale value. Set the
+	 * register to 0 to avoid this.
+	 */
+
+	/* TODO: Check if alpha-blending should be disabled in PnMR. */
+	rcar_du_plane_write(rgrp, index, PnALPHAR, 0);
 }
 
 static void rcar_du_plane_setup_format(struct rcar_du_group *rgrp,