drm/i915: keep backlight_level and backlight device brightness in sync

A single point of truth would be better than two, but achieving that would
require more abstractions for CONFIG_BACKLIGHT_CLASS_DEVICE=n with not a
whole lot of real benefits. Take the short route and just keep the
backlight levels in sync. In particular, update backlight device brightness
on opregion brightness changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_panel.c

@@ -287,6 +287,9 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	dev_priv->backlight_level = level;
+	if (dev_priv->backlight)
+		dev_priv->backlight->props.brightness = level;
+
 	if (dev_priv->backlight_enabled)
 		intel_panel_actually_set_backlight(dev, level);
 }
@@ -318,8 +321,12 @@ void intel_panel_enable_backlight(struct drm_device *dev,
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (dev_priv->backlight_level == 0)
+	if (dev_priv->backlight_level == 0) {
 		dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
+		if (dev_priv->backlight)
+			dev_priv->backlight->props.brightness =
+				dev_priv->backlight_level;
+	}
 
 	dev_priv->backlight_enabled = true;
 	intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
@@ -427,6 +434,7 @@ int intel_panel_setup_backlight(struct drm_connector *connector)
 
 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_RAW;
+	props.brightness = dev_priv->backlight_level;
 	props.max_brightness = _intel_panel_get_max_backlight(dev);
 	if (props.max_brightness == 0) {
 		DRM_DEBUG_DRIVER("Failed to get maximum backlight value\n");
@@ -443,7 +451,6 @@ int intel_panel_setup_backlight(struct drm_connector *connector)
 		dev_priv->backlight = NULL;
 		return -ENODEV;
 	}
-	dev_priv->backlight->props.brightness = intel_panel_get_backlight(dev);
 	return 0;
 }