diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 41156c5370f7..72a2b8cee319 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -223,6 +223,9 @@ find_memend_and_nodes(struct meminfo *mi, struct node_info *np)
 	 * This doesn't seem to be used by the Linux memory
 	 * manager any more.  If we can get rid of it, we
 	 * also get rid of some of the stuff above as well.
+	 *
+	 * Note: max_low_pfn and max_pfn reflect the number
+	 * of _pages_ in the system, not the maximum PFN.
 	 */
 	max_low_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET);
 	max_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET);