drm/i915: ILK + VT-d workaround

Idle the GPU before doing any unmaps. We know if VT-d is in use through
an exported variable from iommu code.

This should avoid a known HW issue.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Keith Packard <keithp@keithp.com>

include/drm/intel-gtt.h

@@ -13,6 +13,8 @@ const struct intel_gtt {
 	unsigned int gtt_mappable_entries;
 	/* Whether i915 needs to use the dmar apis or not. */
 	unsigned int needs_dmar : 1;
+	/* Whether we idle the gpu before mapping/unmapping */
+	unsigned int do_idle_maps : 1;
 } *intel_gtt_get(void);
 
 void intel_gtt_chipset_flush(void);