drm/mediatek: Add display merge start/stop API for cmdq support

Add merge start/stop API for cmdq support. The ovl_adaptor merges
are configured with each drm plane update. Need to enable/disable
merge with cmdq making sure all the settings taken effect in the
same vblank.

Signed-off-by: Nancy.Lin <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Tested-by: AngeloGioacchino Del Regno <[e-mail]>
Tested-by: Bo-Chen Chen <[e-mail]>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/[e-mail]/
Signed-off-by: Chun-Kuang Hu <[e-mail]>

drivers/gpu/drm/mediatek/mtk_disp_drv.h

···
 void mtk_merge_advance_config(struct device *dev, unsigned int l_w, unsigned int r_w,
 			      unsigned int h, unsigned int vrefresh, unsigned int bpc,
 			      struct cmdq_pkt *cmdq_pkt);
+void mtk_merge_start_cmdq(struct device *dev, struct cmdq_pkt *cmdq_pkt);
+void mtk_merge_stop_cmdq(struct device *dev, struct cmdq_pkt *cmdq_pkt);
 
 void mtk_ovl_bgclr_in_on(struct device *dev);
 void mtk_ovl_bgclr_in_off(struct device *dev);

drivers/gpu/drm/mediatek/mtk_disp_merge.c

···
 
 void mtk_merge_start(struct device *dev)
 {
-	struct mtk_disp_merge *priv = dev_get_drvdata(dev);
-
-	writel(MERGE_EN, priv->regs + DISP_REG_MERGE_CTRL);
+	mtk_merge_start_cmdq(dev, NULL);
 }
 
 void mtk_merge_stop(struct device *dev)
 {
+	mtk_merge_stop_cmdq(dev, NULL);
+}
+
+void mtk_merge_start_cmdq(struct device *dev, struct cmdq_pkt *cmdq_pkt)
+{
 	struct mtk_disp_merge *priv = dev_get_drvdata(dev);
 
-	writel(0x0, priv->regs + DISP_REG_MERGE_CTRL);
+	mtk_ddp_write(cmdq_pkt, 1, &priv->cmdq_reg, priv->regs,
+		      DISP_REG_MERGE_CTRL);
+}
+
+void mtk_merge_stop_cmdq(struct device *dev, struct cmdq_pkt *cmdq_pkt)
+{
+	struct mtk_disp_merge *priv = dev_get_drvdata(dev);
+
+	mtk_ddp_write(cmdq_pkt, 0, &priv->cmdq_reg, priv->regs,
+		      DISP_REG_MERGE_CTRL);
 }
 
 static void mtk_merge_fifo_setting(struct mtk_disp_merge *priv,