drm/panel: sitronix-st7789v: 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: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-24-sam@ravnborg.org

drivers/gpu/drm/panel/panel-sitronix-st7789v.c

@@ -3,7 +3,6 @@
  * Copyright (C) 2017 Free Electrons
  */
 
-#include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
@@ -116,7 +115,6 @@ struct st7789v {
 	struct drm_panel panel;
 	struct spi_device *spi;
 	struct gpio_desc *reset;
-	struct backlight_device *backlight;
 	struct regulator *power;
 };
 
@@ -323,12 +321,6 @@ static int st7789v_enable(struct drm_panel *panel)
 {
 	struct st7789v *ctx = panel_to_st7789v(panel);
 
-	if (ctx->backlight) {
-		ctx->backlight->props.state &= ~BL_CORE_FBBLANK;
-		ctx->backlight->props.power = FB_BLANK_UNBLANK;
-		backlight_update_status(ctx->backlight);
-	}
-
 	return st7789v_write_command(ctx, MIPI_DCS_SET_DISPLAY_ON);
 }
 
@@ -339,12 +331,6 @@ static int st7789v_disable(struct drm_panel *panel)
 
 	ST7789V_TEST(ret, st7789v_write_command(ctx, MIPI_DCS_SET_DISPLAY_OFF));
 
-	if (ctx->backlight) {
-		ctx->backlight->props.power = FB_BLANK_POWERDOWN;
-		ctx->backlight->props.state |= BL_CORE_FBBLANK;
-		backlight_update_status(ctx->backlight);
-	}
-
 	return 0;
 }
 
@@ -370,7 +356,6 @@ static const struct drm_panel_funcs st7789v_drm_funcs = {
 
 static int st7789v_probe(struct spi_device *spi)
 {
-	struct device_node *backlight;
 	struct st7789v *ctx;
 	int ret;
 
@@ -394,26 +379,15 @@ static int st7789v_probe(struct spi_device *spi)
 		return PTR_ERR(ctx->reset);
 	}
 
-	backlight = of_parse_phandle(spi->dev.of_node, "backlight", 0);
-	if (backlight) {
-		ctx->backlight = of_find_backlight_by_node(backlight);
-		of_node_put(backlight);
-
-		if (!ctx->backlight)
-			return -EPROBE_DEFER;
-	}
+	ret = drm_panel_of_backlight(&ctx->panel);
+	if (ret)
+		return ret;
 
 	ret = drm_panel_add(&ctx->panel);
 	if (ret < 0)
-		goto err_free_backlight;
+		return ret;
 
 	return 0;
-
-err_free_backlight:
-	if (ctx->backlight)
-		put_device(&ctx->backlight->dev);
-
-	return ret;
 }
 
 static int st7789v_remove(struct spi_device *spi)
@@ -422,9 +396,6 @@ static int st7789v_remove(struct spi_device *spi)
 
 	drm_panel_remove(&ctx->panel);
 
-	if (ctx->backlight)
-		put_device(&ctx->backlight->dev);
-
 	return 0;
 }