drm/panel: sitronix-st7701: use drm_panel backlight support

Use the backlight support in drm_panel to simplify the driver
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-23-sam@ravnborg.org

drivers/gpu/drm/panel/panel-sitronix-st7701.c

@@ -9,7 +9,6 @@
 #include <drm/drm_panel.h>
 #include <drm/drm_print.h>
 
-#include <linux/backlight.h>
 #include <linux/gpio/consumer.h>
 #include <linux/delay.h>
 #include <linux/module.h>
@@ -103,7 +102,6 @@ struct st7701 {
 	struct mipi_dsi_device *dsi;
 	const struct st7701_panel_desc *desc;
 
-	struct backlight_device *backlight;
 	struct regulator_bulk_data *supplies;
 	struct gpio_desc *reset;
 	unsigned int sleep_delay;
@@ -223,7 +221,6 @@ static int st7701_enable(struct drm_panel *panel)
 	struct st7701 *st7701 = panel_to_st7701(panel);
 
 	ST7701_DSI(st7701, MIPI_DCS_SET_DISPLAY_ON, 0x00);
-	backlight_enable(st7701->backlight);
 
 	return 0;
 }
@@ -232,7 +229,6 @@ static int st7701_disable(struct drm_panel *panel)
 {
 	struct st7701 *st7701 = panel_to_st7701(panel);
 
-	backlight_disable(st7701->backlight);
 	ST7701_DSI(st7701, MIPI_DCS_SET_DISPLAY_OFF, 0x00);
 
 	return 0;
@@ -366,10 +362,6 @@ static int st7701_dsi_probe(struct mipi_dsi_device *dsi)
 		return PTR_ERR(st7701->reset);
 	}
 
-	st7701->backlight = devm_of_find_backlight(&dsi->dev);
-	if (IS_ERR(st7701->backlight))
-		return PTR_ERR(st7701->backlight);
-
 	drm_panel_init(&st7701->panel, &dsi->dev, &st7701_funcs,
 		       DRM_MODE_CONNECTOR_DSI);
 
@@ -384,6 +376,10 @@ static int st7701_dsi_probe(struct mipi_dsi_device *dsi)
 	 */
 	st7701->sleep_delay = 120 + desc->panel_sleep_delay;
 
+	ret = drm_panel_of_backlight(&st7701->panel);
+	if (ret)
+		return ret;
+
 	ret = drm_panel_add(&st7701->panel);
 	if (ret < 0)
 		return ret;