drm/mediatek: Enable dither function

Enable dither function to improve the display quality.
Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c

@@ -53,6 +53,7 @@
 #define DITHER_EN				BIT(0)
 #define DISP_DITHER_CFG				0x0020
 #define DITHER_RELAY_MODE			BIT(0)
+#define DITHER_ENGINE_EN			BIT(1)
 #define DISP_DITHER_SIZE			0x0030
 
 #define LUT_10BIT_MASK				0x03ff
@@ -317,6 +318,8 @@ static void mtk_dither_config(struct device *dev, unsigned int w,
 
 	mtk_ddp_write(cmdq_pkt, h << 16 | w, &priv->cmdq_reg, priv->regs, DISP_DITHER_SIZE);
 	mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, &priv->cmdq_reg, priv->regs, DISP_DITHER_CFG);
+	mtk_dither_set_common(priv->regs, &priv->cmdq_reg, bpc, DISP_DITHER_CFG,
+			      DITHER_ENGINE_EN, cmdq_pkt);
 }
 
 static void mtk_dither_start(struct device *dev)