diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index 0c35a88e33dd..98c8b5b7627b 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -951,10 +951,27 @@ static void vop_crtc_atomic_enable(struct drm_crtc *crtc,
 	    !(vop_data->feature & VOP_FEATURE_OUTPUT_RGB10))
 		s->output_mode = ROCKCHIP_OUT_MODE_P888;
 
-	if (s->output_mode == ROCKCHIP_OUT_MODE_AAAA && s->output_bpc == 8)
-		VOP_REG_SET(vop, common, pre_dither_down, 1);
-	else
-		VOP_REG_SET(vop, common, pre_dither_down, 0);
+	if (s->output_bpc) { /* Only dither if bpc known. */
+		if (vop_data->feature & VOP_FEATURE_OUTPUT_RGB10) {
+			if (s->output_mode == ROCKCHIP_OUT_MODE_AAAA && s->output_bpc <= 8)
+				VOP_REG_SET(vop, common, pre_dither_down, 1);
+			else
+				VOP_REG_SET(vop, common, pre_dither_down, 0);
+		}
+		if (s->output_bpc == 6) {
+			/* Enable allegro dither to RGB666 */
+			VOP_REG_SET(vop, common, dither_down_sel, DITHER_DOWN_ALLEGRO);
+			VOP_REG_SET(vop, common, dither_down_mode, RGB888_TO_RGB666);
+			VOP_REG_SET(vop, common, dither_down_en, 1);
+		} else {
+			VOP_REG_SET(vop, common, dither_down_en, 0);
+		}
+	} else {
+		if (vop_data->feature & VOP_FEATURE_OUTPUT_RGB10)
+			VOP_REG_SET(vop, common, pre_dither_down, 0);
+
+		VOP_REG_SET(vop, common, dither_down_en, 0);
+	}
 
 	VOP_REG_SET(vop, common, out_mode, s->output_mode);
 
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
index fd5765dfd637..92050de140b6 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
@@ -68,7 +68,9 @@ struct vop_common {
 	struct vop_reg dsp_blank;
 	struct vop_reg data_blank;
 	struct vop_reg pre_dither_down;
-	struct vop_reg dither_down;
+	struct vop_reg dither_down_sel;
+	struct vop_reg dither_down_mode;
+	struct vop_reg dither_down_en;
 	struct vop_reg dither_up;
 	struct vop_reg gate_en;
 	struct vop_reg mmu_en;
@@ -268,6 +270,16 @@ enum scale_down_mode {
 	SCALE_DOWN_AVG = 0x1
 };
 
+enum dither_down_mode {
+	RGB888_TO_RGB565 = 0x0,
+	RGB888_TO_RGB666 = 0x1
+};
+
+enum dither_down_mode_sel {
+	DITHER_DOWN_ALLEGRO = 0x0,
+	DITHER_DOWN_FRC = 0x1
+};
+
 enum vop_pol {
 	HSYNC_POSITIVE = 0,
 	VSYNC_POSITIVE = 1,
diff --git a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
index a6db3cd5544b..59266c473795 100644
--- a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
+++ b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
@@ -137,6 +137,9 @@ static const struct vop_common rk3036_common = {
 	.standby = VOP_REG_SYNC(RK3036_SYS_CTRL, 0x1, 30),
 	.out_mode = VOP_REG(RK3036_DSP_CTRL0, 0xf, 0),
 	.dsp_blank = VOP_REG(RK3036_DSP_CTRL1, 0x1, 24),
+	.dither_down_sel = VOP_REG(RK3036_DSP_CTRL0, 0x1, 27),
+	.dither_down_en = VOP_REG(RK3036_DSP_CTRL0, 0x1, 11),
+	.dither_down_mode = VOP_REG(RK3036_DSP_CTRL0, 0x1, 10),
 	.cfg_done = VOP_REG_SYNC(RK3036_REG_CFG_DONE, 0x1, 0),
 };
 
@@ -200,6 +203,9 @@ static const struct vop_common px30_common = {
 	.standby = VOP_REG_SYNC(PX30_SYS_CTRL2, 0x1, 1),
 	.out_mode = VOP_REG(PX30_DSP_CTRL2, 0xf, 16),
 	.dsp_blank = VOP_REG(PX30_DSP_CTRL2, 0x1, 14),
+	.dither_down_en = VOP_REG(PX30_DSP_CTRL2, 0x1, 8),
+	.dither_down_sel = VOP_REG(PX30_DSP_CTRL2, 0x1, 7),
+	.dither_down_mode = VOP_REG(PX30_DSP_CTRL2, 0x1, 6),
 	.cfg_done = VOP_REG_SYNC(PX30_REG_CFG_DONE, 0x1, 0),
 };
 
@@ -350,6 +356,9 @@ static const struct vop_common rk3188_common = {
 	.standby = VOP_REG(RK3188_SYS_CTRL, 0x1, 30),
 	.out_mode = VOP_REG(RK3188_DSP_CTRL0, 0xf, 0),
 	.cfg_done = VOP_REG(RK3188_REG_CFG_DONE, 0x1, 0),
+	.dither_down_sel = VOP_REG(RK3188_DSP_CTRL0, 0x1, 27),
+	.dither_down_en = VOP_REG(RK3188_DSP_CTRL0, 0x1, 11),
+	.dither_down_mode = VOP_REG(RK3188_DSP_CTRL0, 0x1, 10),
 	.dsp_blank = VOP_REG(RK3188_DSP_CTRL1, 0x3, 24),
 };
 
@@ -473,8 +482,10 @@ static const struct vop_common rk3288_common = {
 	.standby = VOP_REG_SYNC(RK3288_SYS_CTRL, 0x1, 22),
 	.gate_en = VOP_REG(RK3288_SYS_CTRL, 0x1, 23),
 	.mmu_en = VOP_REG(RK3288_SYS_CTRL, 0x1, 20),
+	.dither_down_sel = VOP_REG(RK3288_DSP_CTRL1, 0x1, 4),
+	.dither_down_mode = VOP_REG(RK3288_DSP_CTRL1, 0x1, 3),
+	.dither_down_en = VOP_REG(RK3288_DSP_CTRL1, 0x1, 2),
 	.pre_dither_down = VOP_REG(RK3288_DSP_CTRL1, 0x1, 1),
-	.dither_down = VOP_REG(RK3288_DSP_CTRL1, 0xf, 1),
 	.dither_up = VOP_REG(RK3288_DSP_CTRL1, 0x1, 6),
 	.data_blank = VOP_REG(RK3288_DSP_CTRL0, 0x1, 19),
 	.dsp_blank = VOP_REG(RK3288_DSP_CTRL0, 0x3, 18),
@@ -707,7 +718,10 @@ static const struct vop_misc rk3328_misc = {
 
 static const struct vop_common rk3328_common = {
 	.standby = VOP_REG_SYNC(RK3328_SYS_CTRL, 0x1, 22),
-	.dither_down = VOP_REG(RK3328_DSP_CTRL1, 0xf, 1),
+	.dither_down_sel = VOP_REG(RK3328_DSP_CTRL1, 0x1, 4),
+	.dither_down_mode = VOP_REG(RK3328_DSP_CTRL1, 0x1, 3),
+	.dither_down_en = VOP_REG(RK3328_DSP_CTRL1, 0x1, 2),
+	.pre_dither_down = VOP_REG(RK3328_DSP_CTRL1, 0x1, 1),
 	.dither_up = VOP_REG(RK3328_DSP_CTRL1, 0x1, 6),
 	.dsp_blank = VOP_REG(RK3328_DSP_CTRL0, 0x3, 18),
 	.out_mode = VOP_REG(RK3328_DSP_CTRL0, 0xf, 0),
