diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 0cf3a4e..3af4ffd 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -21,6 +21,7 @@
 
 #define IOMMU_READ	(1)
 #define IOMMU_WRITE	(2)
+#define IOMMU_CACHE	(4) /* DMA cache coherency */
 
 struct device;