drm/i915: fix suspend/resume breakage in lid notifier

We now unconditionally restore the mode at lid open time since some
platforms turn off the panel, pipes or other display elements when the
lid is closed.  There's a problem with doing this at resume time
however.

At resume time, we'll get a lid event, but restoring the mode at that
time may not be safe (e.g. if we get the lid event before global state
has been restored), so check the suspended state and make sure our
restore is locked against other mode updates.

Tested-by: Ben Gamari <bgamari.foss@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/gpu/drm/i915/i915_drv.c

@@ -89,6 +89,8 @@ static int i915_suspend(struct drm_device *dev, pm_message_t state)
 		pci_set_power_state(dev->pdev, PCI_D3hot);
 	}
 
+	dev_priv->suspended = 1;
+
 	return 0;
 }
 
@@ -124,6 +126,8 @@ static int i915_resume(struct drm_device *dev)
 		drm_helper_resume_force_mode(dev);
 	}
 
+	dev_priv->suspended = 0;
+
 	return ret;
 }
 

drivers/gpu/drm/i915/i915_drv.h

@@ -253,6 +253,7 @@ typedef struct drm_i915_private {
 	struct workqueue_struct *wq;
 
 	/* Register state */
+	bool suspended;
 	u8 saveLBB;
 	u32 saveDSPACNTR;
 	u32 saveDSPBCNTR;

drivers/gpu/drm/i915/intel_lvds.c

@@ -651,8 +651,11 @@ static int intel_lid_notify(struct notifier_block *nb, unsigned long val,
 		container_of(nb, struct drm_i915_private, lid_notifier);
 	struct drm_device *dev = dev_priv->dev;
 
-	if (acpi_lid_open())
+	if (acpi_lid_open() && !dev_priv->suspended) {
+		mutex_lock(&dev->mode_config.mutex);
 		drm_helper_resume_force_mode(dev);
+		mutex_unlock(&dev->mode_config.mutex);
+	}
 
 	drm_sysfs_hotplug_event(dev_priv->dev);