diff --git a/bindings/iommu/arm,smmu.txt b/bindings/iommu/arm,smmu.txt
index ea2fa346..c886bfb6 100644
--- a/bindings/iommu/arm,smmu.txt
+++ b/bindings/iommu/arm,smmu.txt
@@ -243,10 +243,12 @@ conditions.
 --- "coherent"
 		Pagetables are io-coherent.
 --- "LLC"
-		Pagetables may be saved in the system cache.
+		Pagetables may be saved in the system cache. Should not be used if
+		the IOMMU device is io-coherent.
 --- "LLC_NWA"
 		Pagetables may be saved in the system cache is used, and
-		 write-allocate hint is disabled.
+		write-allocate hint is disabled. Should not be used if the IOMMU
+		device is io-coherent.
 
 - qcom,iommu-earlymap:
 		Optional, Bool.