diff --git a/arch/arm/kernel/io.c b/arch/arm/kernel/io.c
index 6c20c1188b60..1f6822dfae74 100644
--- a/arch/arm/kernel/io.c
+++ b/arch/arm/kernel/io.c
@@ -7,7 +7,7 @@
  * Copy data from IO memory space to "real" memory space.
  * This needs to be optimized.
  */
-void _memcpy_fromio(void *to, void __iomem *from, size_t count)
+void _memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
 {
 	unsigned char *t = to;
 	while (count) {
@@ -22,7 +22,7 @@ void _memcpy_fromio(void *to, void __iomem *from, size_t count)
  * Copy data from "real" memory space to IO memory space.
  * This needs to be optimized.
  */
-void _memcpy_toio(void __iomem *to, const void *from, size_t count)
+void _memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
 {
 	const unsigned char *f = from;
 	while (count) {
@@ -37,7 +37,7 @@ void _memcpy_toio(void __iomem *to, const void *from, size_t count)
  * "memset" on IO memory space.
  * This needs to be optimized.
  */
-void _memset_io(void __iomem *dst, int c, size_t count)
+void _memset_io(volatile void __iomem *dst, int c, size_t count)
 {
 	while (count) {
 		count--;
diff --git a/include/asm-arm/io.h b/include/asm-arm/io.h
index cfa71a0dffb6..5c4ae8f5dbb0 100644
--- a/include/asm-arm/io.h
+++ b/include/asm-arm/io.h
@@ -136,9 +136,9 @@ extern void __readwrite_bug(const char *fn);
 /*
  * String version of IO memory access ops:
  */
-extern void _memcpy_fromio(void *, void __iomem *, size_t);
-extern void _memcpy_toio(void __iomem *, const void *, size_t);
-extern void _memset_io(void __iomem *, int, size_t);
+extern void _memcpy_fromio(void *, const volatile void __iomem *, size_t);
+extern void _memcpy_toio(volatile void __iomem *, const void *, size_t);
+extern void _memset_io(volatile void __iomem *, int, size_t);
 
 #define mmiowb()