drm/i915: ensure single initialization and cleanup of backlight device

commit dc652f90e088798bfa31f496ba994ddadd5d5680 upstream.

Backlight cleanup in the eDP connector destroy callback caused the
backlight device to be removed on some systems that first initialized LVDS
and then attempted to initialize eDP. Prevent multiple backlight
initializations, and ensure backlight cleanup is only done once by moving
it to modeset cleanup.

A small wrinkle is the introduced asymmetry in backlight
setup/cleanup. This could be solved by adding refcounting, but it seems
overkill considering that there should only ever be one backlight device.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=55701
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Peter Verthez <peter.verthez@skynet.be>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2:
 - Adjust context
 - s/dev_priv->backlight\.device/dev_priv->backlight/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

4 files changed, 9 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 897ca06f424..cfbb893f4e8 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9093,6 +9093,9 @@ void intel_modeset_cleanup(struct drm_device *dev)
 	del_timer_sync(&dev_priv->idle_timer);
 	cancel_work_sync(&dev_priv->idle_work);
 
+	/* destroy backlight, if any, before the connectors */
+	intel_panel_destroy_backlight(dev);
+
 	drm_mode_config_cleanup(dev);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index c8ecaabe7be..a07ccab3401 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2274,11 +2274,6 @@ done:
 static void
 intel_dp_destroy(struct drm_connector *connector)
 {
-	struct drm_device *dev = connector->dev;
-
-	if (intel_dpd_is_edp(dev))
-		intel_panel_destroy_backlight(dev);
-
 	drm_sysfs_connector_remove(connector);
 	drm_connector_cleanup(connector);
 	kfree(connector);
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index a8b29fd529e..876bac03562 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -553,8 +553,6 @@ static void intel_lvds_destroy(struct drm_connector *connector)
 	struct drm_device *dev = connector->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	intel_panel_destroy_backlight(dev);
-
 	if (dev_priv->lid_notifier.notifier_call)
 		acpi_lid_notifier_unregister(&dev_priv->lid_notifier);
 	drm_sysfs_connector_remove(connector);
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 72b89490316..04cb34a37e9 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -361,6 +361,9 @@ int intel_panel_setup_backlight(struct drm_device *dev)
 
 	intel_panel_init_backlight(dev);
 
+	if (WARN_ON(dev_priv->backlight))
+		return -ENODEV;
+
 	if (dev_priv->int_lvds_connector)
 		connector = dev_priv->int_lvds_connector;
 	else if (dev_priv->int_edp_connector)
@@ -388,8 +391,10 @@ int intel_panel_setup_backlight(struct drm_device *dev)
 void intel_panel_destroy_backlight(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	if (dev_priv->backlight)
+	if (dev_priv->backlight) {
 		backlight_device_unregister(dev_priv->backlight);
+		dev_priv->backlight = NULL;
+	}
 }
 #else
 int intel_panel_setup_backlight(struct drm_device *dev)