drm: rcar-du: dsi: Improve DSI shutdown

Improve the DSI shutdown procedure by clearing various bits that were
set while enabling the DSI output. There has been no clear issues caused
by these, but it's safer to ensure that the features are disabled at the
start of the next DSI enable.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c

@@ -441,9 +441,21 @@ static int rcar_mipi_dsi_startup(struct rcar_mipi_dsi *dsi,
 
 static void rcar_mipi_dsi_shutdown(struct rcar_mipi_dsi *dsi)
 {
+	/* Disable VCLKEN */
+	rcar_mipi_dsi_write(dsi, VCLKSET, 0);
+
+	/* Disable DOT clock */
+	rcar_mipi_dsi_write(dsi, VCLKSET, 0);
+
 	rcar_mipi_dsi_clr(dsi, PHYSETUP, PHYSETUP_RSTZ);
 	rcar_mipi_dsi_clr(dsi, PHYSETUP, PHYSETUP_SHUTDOWNZ);
 
+	/* CFGCLK disable */
+	rcar_mipi_dsi_clr(dsi, CFGCLKSET, CFGCLKSET_CKEN);
+
+	/* LPCLK disable */
+	rcar_mipi_dsi_clr(dsi, LPCLKSET, LPCLKSET_CKEN);
+
 	dev_dbg(dsi->dev, "DSI device is shutdown\n");
 }