drm/i915: gen4: work around hang during hibernation

Bjørn reported that his machine hang during hibernation and eventually
bisected the problem to the following commit:

commit da2bc1b9db3351addd293e5b82757efe1f77ed1d
Author: Imre Deak <imre.deak@intel.com>
Date:   Thu Oct 23 19:23:26 2014 +0300

    drm/i915: add poweroff_late handler

The problem seems to be that after the kernel puts the device into D3
the BIOS still tries to access it, or otherwise assumes that it's in D0.
This is clearly bogus, since ACPI mandates that devices are put into D3
by the OSPM if they are not wake-up sources. In the future we want to
unify more of the driver's runtime and system suspend paths, for example
by skipping all the system suspend/hibernation hooks if the device is
runtime suspended already. Accordingly for all other platforms the goal
is still to properly power down the device during hibernation.

v2:
- Another GEN4 Lenovo laptop had the same issue, while platforms from
  other vendors (including mobile and desktop, GEN4 and non-GEN4) seem
  to work fine. Based on this apply the workaround on all GEN4 Lenovo
  platforms.
- add code comment about failing platforms (Ville)

Reference: http://lists.freedesktop.org/archives/intel-gfx/2015-February/060633.html
Reported-and-bisected-by: Bjørn Mork <bjorn@mork.no>
Cc: stable@vger.kernel.org # v3.19
Signed-off-by: Imre Deak <imre.deak@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -622,7 +622,7 @@ static int i915_drm_suspend(struct drm_device *dev)
 	return 0;
 }
 
-static int i915_drm_suspend_late(struct drm_device *drm_dev)
+static int i915_drm_suspend_late(struct drm_device *drm_dev, bool hibernation)
 {
 	struct drm_i915_private *dev_priv = drm_dev->dev_private;
 	int ret;
@@ -636,7 +636,17 @@ static int i915_drm_suspend_late(struct drm_device *drm_dev)
 	}
 
 	pci_disable_device(drm_dev->pdev);
-	pci_set_power_state(drm_dev->pdev, PCI_D3hot);
+	/*
+	 * During hibernation on some GEN4 platforms the BIOS may try to access
+	 * the device even though it's already in D3 and hang the machine. So
+	 * leave the device in D0 on those platforms and hope the BIOS will
+	 * power down the device properly. Platforms where this was seen:
+	 * Lenovo Thinkpad X301, X61s
+	 */
+	if (!(hibernation &&
+	      drm_dev->pdev->subsystem_vendor == PCI_VENDOR_ID_LENOVO &&
+	      INTEL_INFO(dev_priv)->gen == 4))
+		pci_set_power_state(drm_dev->pdev, PCI_D3hot);
 
 	return 0;
 }
@@ -662,7 +672,7 @@ int i915_suspend_legacy(struct drm_device *dev, pm_message_t state)
 	if (error)
 		return error;
 
-	return i915_drm_suspend_late(dev);
+	return i915_drm_suspend_late(dev, false);
 }
 
 static int i915_drm_resume(struct drm_device *dev)
@@ -950,7 +960,17 @@ static int i915_pm_suspend_late(struct device *dev)
 	if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF)
 		return 0;
 
-	return i915_drm_suspend_late(drm_dev);
+	return i915_drm_suspend_late(drm_dev, false);
+}
+
+static int i915_pm_poweroff_late(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_to_i915(dev)->dev;
+
+	if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF)
+		return 0;
+
+	return i915_drm_suspend_late(drm_dev, true);
 }
 
 static int i915_pm_resume_early(struct device *dev)
@@ -1520,7 +1540,7 @@ static const struct dev_pm_ops i915_pm_ops = {
 	.thaw_early = i915_pm_resume_early,
 	.thaw = i915_pm_resume,
 	.poweroff = i915_pm_suspend,
-	.poweroff_late = i915_pm_suspend_late,
+	.poweroff_late = i915_pm_poweroff_late,
 	.restore_early = i915_pm_resume_early,
 	.restore = i915_pm_resume,