drm/panel: panel-dsi-cm: Use backlight helpers

Instead of retrieving the backlight brightness in struct
backlight_properties manually, and then checking whether the backlight
should be on at all, use backlight_get_brightness() which does all
this and insulates this from future changes.

Instead of setting the power state by manually updating fields in
struct backlight_properties, use backlight_enable() and
backlight_disable(). These also call backlight_update_status() so the
separate call is no longer needed.

Signed-off-by: Stephen Kitt <steve@sk2.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220616172316.1355133-3-steve@sk2.org

drivers/gpu/drm/panel/panel-dsi-cm.c

@@ -85,17 +85,10 @@ static void dsicm_bl_power(struct panel_drv_data *ddata, bool enable)
 	else
 		return;
 
-	if (enable) {
+	if (enable)
-		backlight->props.fb_blank = FB_BLANK_UNBLANK;
+		backlight_enable(backlight);
-		backlight->props.state = ~(BL_CORE_FBBLANK | BL_CORE_SUSPENDED);
+	else
-		backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_disable(backlight);
-	} else {
-		backlight->props.fb_blank = FB_BLANK_NORMAL;
-		backlight->props.power = FB_BLANK_POWERDOWN;
-		backlight->props.state |= BL_CORE_FBBLANK | BL_CORE_SUSPENDED;
-	}
-
-	backlight_update_status(backlight);
 }
 
 static void hw_guard_start(struct panel_drv_data *ddata, int guard_msec)
@@ -196,13 +189,7 @@ static int dsicm_bl_update_status(struct backlight_device *dev)
 {
 	struct panel_drv_data *ddata = dev_get_drvdata(&dev->dev);
 	int r = 0;
-	int level;
+	int level = backlight_get_brightness(dev);
-
-	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
-			dev->props.power == FB_BLANK_UNBLANK)
-		level = dev->props.brightness;
-	else
-		level = 0;
 
 	dev_dbg(&ddata->dsi->dev, "update brightness to %d\n", level);
 
@@ -219,11 +206,7 @@ static int dsicm_bl_update_status(struct backlight_device *dev)
 
 static int dsicm_bl_get_intensity(struct backlight_device *dev)
 {
-	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
+	return backlight_get_brightness(dev);
-			dev->props.power == FB_BLANK_UNBLANK)
-		return dev->props.brightness;
-
-	return 0;
 }
 
 static const struct backlight_ops dsicm_bl_ops = {