diff --git a/arch/arm/plat-omap/iopgtable.h b/arch/arm/plat-omap/iopgtable.h
index 37dac434c7a1..ab23b6a140fd 100644
--- a/arch/arm/plat-omap/iopgtable.h
+++ b/arch/arm/plat-omap/iopgtable.h
@@ -1,7 +1,7 @@
 /*
  * omap iommu: pagetable definitions
  *
- * Copyright (C) 2008-2009 Nokia Corporation
+ * Copyright (C) 2008-2010 Nokia Corporation
  *
  * Written by Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
  *
@@ -13,26 +13,52 @@
 #ifndef __PLAT_OMAP_IOMMU_H
 #define __PLAT_OMAP_IOMMU_H
 
+/*
+ * "L2 table" address mask and size definitions.
+ */
 #define IOPGD_SHIFT		20
-#define IOPGD_SIZE		(1 << IOPGD_SHIFT)
+#define IOPGD_SIZE		(1UL << IOPGD_SHIFT)
 #define IOPGD_MASK		(~(IOPGD_SIZE - 1))
-#define IOSECTION_MASK		IOPGD_MASK
-#define PTRS_PER_IOPGD		(1 << (32 - IOPGD_SHIFT))
-#define IOPGD_TABLE_SIZE	(PTRS_PER_IOPGD * sizeof(u32))
 
-#define IOSUPER_SIZE		(IOPGD_SIZE << 4)
+/*
+ * "section" address mask and size definitions.
+ */
+#define IOSECTION_SHIFT		20
+#define IOSECTION_SIZE		(1UL << IOSECTION_SHIFT)
+#define IOSECTION_MASK		(~(IOSECTION_SIZE - 1))
+
+/*
+ * "supersection" address mask and size definitions.
+ */
+#define IOSUPER_SHIFT		24
+#define IOSUPER_SIZE		(1UL << IOSUPER_SHIFT)
 #define IOSUPER_MASK		(~(IOSUPER_SIZE - 1))
 
-#define IOPTE_SHIFT		12
-#define IOPTE_SIZE		(1 << IOPTE_SHIFT)
-#define IOPTE_MASK		(~(IOPTE_SIZE - 1))
-#define IOPAGE_MASK		IOPTE_MASK
-#define PTRS_PER_IOPTE		(1 << (IOPGD_SHIFT - IOPTE_SHIFT))
-#define IOPTE_TABLE_SIZE	(PTRS_PER_IOPTE * sizeof(u32))
+#define PTRS_PER_IOPGD		(1UL << (32 - IOPGD_SHIFT))
+#define IOPGD_TABLE_SIZE	(PTRS_PER_IOPGD * sizeof(u32))
 
-#define IOLARGE_SIZE		(IOPTE_SIZE << 4)
+/*
+ * "small page" address mask and size definitions.
+ */
+#define IOPTE_SHIFT		12
+#define IOPTE_SIZE		(1UL << IOPTE_SHIFT)
+#define IOPTE_MASK		(~(IOPTE_SIZE - 1))
+
+/*
+ * "large page" address mask and size definitions.
+ */
+#define IOLARGE_SHIFT		16
+#define IOLARGE_SIZE		(1UL << IOLARGE_SHIFT)
 #define IOLARGE_MASK		(~(IOLARGE_SIZE - 1))
 
+#define PTRS_PER_IOPTE		(1UL << (IOPGD_SHIFT - IOPTE_SHIFT))
+#define IOPTE_TABLE_SIZE	(PTRS_PER_IOPTE * sizeof(u32))
+
+#define IOPAGE_MASK		IOPTE_MASK
+
+/*
+ * some descriptor attributes.
+ */
 #define IOPGD_TABLE		(1 << 0)
 #define IOPGD_SECTION		(2 << 0)
 #define IOPGD_SUPER		(1 << 18 | 2 << 0)
@@ -40,12 +66,14 @@
 #define IOPTE_SMALL		(2 << 0)
 #define IOPTE_LARGE		(1 << 0)
 
+/* to find an entry in a page-table-directory */
 #define iopgd_index(da)		(((da) >> IOPGD_SHIFT) & (PTRS_PER_IOPGD - 1))
 #define iopgd_offset(obj, da)	((obj)->iopgd + iopgd_index(da))
 
 #define iopte_paddr(iopgd)	(*iopgd & ~((1 << 10) - 1))
 #define iopte_vaddr(iopgd)	((u32 *)phys_to_virt(iopte_paddr(iopgd)))
 
+/* to find an entry in the second-level page table. */
 #define iopte_index(da)		(((da) >> IOPTE_SHIFT) & (PTRS_PER_IOPTE - 1))
 #define iopte_offset(iopgd, da)	(iopte_vaddr(iopgd) + iopte_index(da))