drm/i915/bdw: Restore PPAT on thaw

Apparently it is wiped out from under us, and we get some really fun
caching artifacts upon resume (it seems to be WB for all types by
default).

Reported-by: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Tested-by: James Ausmus <james.ausmus@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76113
Tested-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -30,6 +30,8 @@
 #include "i915_trace.h"
 #include "intel_drv.h"
 
+static void gen8_setup_private_ppat(struct drm_i915_private *dev_priv);
+
 bool intel_enable_ppgtt(struct drm_device *dev, bool full)
 {
 	if (i915.enable_ppgtt == 0 || !HAS_ALIASING_PPGTT(dev))
@@ -1370,8 +1372,10 @@ void i915_gem_restore_gtt_mappings(struct drm_device *dev)
 	}
 
 
-	if (INTEL_INFO(dev)->gen >= 8)
+	if (INTEL_INFO(dev)->gen >= 8) {
+		gen8_setup_private_ppat(dev_priv);
 		return;
+	}
 
 	list_for_each_entry(vm, &dev_priv->vm_list, global_link) {
 		/* TODO: Perhaps it shouldn't be gen6 specific */