drm/mediatek: add dsi reg commit disable control

New DSI IP has shadow register and working reg. The register
values are writen to shadow register. And then trigger with
commit reg, the register values will be moved working register.

This function is default on. But this driver doesn't use this
function. So add the disable control.
Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_dsi.c

@@ -125,6 +125,10 @@
 #define VM_CMD_EN			BIT(0)
 #define TS_VFP_EN			BIT(5)
 
+#define DSI_SHADOW_DEBUG	0x190U
+#define FORCE_COMMIT			BIT(0)
+#define BYPASS_SHADOW			BIT(1)
+
 #define CONFIG				(0xff << 0)
 #define SHORT_PACKET			0
 #define LONG_PACKET			2
@@ -151,6 +155,7 @@ struct phy;
 
 struct mtk_dsi_driver_data {
 	const u32 reg_cmdq_off;
+	bool has_shadow_ctl;
 };
 
 struct mtk_dsi {
@@ -588,6 +593,11 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
 	}
 
 	mtk_dsi_enable(dsi);
+
+	if (dsi->driver_data->has_shadow_ctl)
+		writel(FORCE_COMMIT | BYPASS_SHADOW,
+		       dsi->regs + DSI_SHADOW_DEBUG);
+
 	mtk_dsi_reset_engine(dsi);
 	mtk_dsi_phy_timconfig(dsi);