+/* Certain Gen5 chipsets require require idling the GPU before
+ * unmapping anything from the GTT when VT-d is enabled.
+ */
+static inline int needs_ilk_vtd_wa(void)
+{
+#ifdef CONFIG_INTEL_IOMMU
+ const unsigned short gpu_devid = intel_private.pcidev->device;
+
+ /* Query intel_iommu to see if we need the workaround. Presumably that
+ * was loaded first.
+ */
+ if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB ||
+ gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
+ intel_iommu_gfx_mapped)
+ return 1;
+#endif
+ return 0;
+}
+
+static bool intel_gtt_can_wc(void)
+{
+ if (INTEL_GTT_GEN <= 2)
+ return false;
+
+ if (INTEL_GTT_GEN >= 6)
+ return false;
+
+ /* Reports of major corruption with ILK vt'd enabled */
+ if (needs_ilk_vtd_wa())
+ return false;
+
+ return true;
+}
+