drm/i915: Disable output polling across suspend & resume

Suspending (especially hibernating) may take a finite amount of time,
during which a hotplug event may trigger and we will attempt to handle
it with inconsistent state. Disable hotplug polling around suspend and
resume.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=30070
Reported-by: Rui Tiago Matos <tiagomatos@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_dma.c

@@ -1172,10 +1172,8 @@ static void i915_switcheroo_set_state(struct pci_dev *pdev, enum vga_switcheroo_
 		/* i915 resume handler doesn't set to D0 */
 		pci_set_power_state(dev->pdev, PCI_D0);
 		i915_resume(dev);
-		drm_kms_helper_poll_enable(dev);
 	} else {
 		printk(KERN_ERR "i915: switched off\n");
-		drm_kms_helper_poll_disable(dev);
 		i915_suspend(dev, pmm);
 	}
 }

drivers/gpu/drm/i915/i915_drv.c

@@ -281,6 +281,8 @@ int i915_suspend(struct drm_device *dev, pm_message_t state)
 	if (state.event == PM_EVENT_PRETHAW)
 		return 0;
 
+	drm_kms_helper_poll_disable(dev);
+
 	error = i915_drm_freeze(dev);
 	if (error)
 		return error;
@@ -325,12 +327,19 @@ static int i915_drm_thaw(struct drm_device *dev)
 
 int i915_resume(struct drm_device *dev)
 {
+	int ret;
+
 	if (pci_enable_device(dev->pdev))
 		return -EIO;
 
 	pci_set_master(dev->pdev);
 
-	return i915_drm_thaw(dev);
+	ret = i915_drm_thaw(dev);
+	if (ret)
+		return ret;
+
+	drm_kms_helper_poll_enable(dev);
+	return 0;
 }
 
 static int i965_reset_complete(struct drm_device *dev)