gpu/drm, x86, PAT: Handle io_mapping_create_wc() errors in a clean way

io_mapping_create_wc can return NULL on error and io_mapping_free() should be
called on one of the error-cleanup path.
Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

drivers/gpu/drm/i915/i915_dma.c

@@ -1090,6 +1090,11 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
         dev_priv->mm.gtt_mapping =
 		io_mapping_create_wc(dev->agp->base,
 				     dev->agp->agp_info.aper_size * 1024*1024);
+	if (dev_priv->mm.gtt_mapping == NULL) {
+		ret = -EIO;
+		goto out_rmmap;
+	}
+
 	/* Set up a WC MTRR for non-PAT systems.  This is more common than
 	 * one would think, because the kernel disables PAT on first
 	 * generation Core chips because WC PAT gets overridden by a UC
@@ -1122,7 +1127,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	if (!I915_NEED_GFX_HWS(dev)) {
 		ret = i915_init_phys_hws(dev);
 		if (ret != 0)
-			goto out_rmmap;
+			goto out_iomapfree;
 	}
 
 	/* On the 945G/GM, the chipset reports the MSI capability on the
@@ -1161,6 +1166,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 
 	return 0;
 
+out_iomapfree:
+	io_mapping_free(dev_priv->mm.gtt_mapping);
 out_rmmap:
 	iounmap(dev_priv->regs);
 free_priv: