diff --git a/arch/mips/mm/ioremap.c b/arch/mips/mm/ioremap.c
index 3101d1d..cea7d0e 100644
--- a/arch/mips/mm/ioremap.c
+++ b/arch/mips/mm/ioremap.c
@@ -176,7 +176,7 @@
 
 #define IS_KSEG1(addr) (((unsigned long)(addr) & ~0x1fffffffUL) == CKSEG1)
 
-void __iounmap(volatile void __iomem *addr)
+void __iounmap(const volatile void __iomem *addr)
 {
 	struct vm_struct *p;
 
diff --git a/include/asm-mips/io.h b/include/asm-mips/io.h
index c2d124b..bc5f3c5 100644
--- a/include/asm-mips/io.h
+++ b/include/asm-mips/io.h
@@ -172,7 +172,7 @@
 #define page_to_phys(page)	((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)
 
 extern void __iomem * __ioremap(phys_t offset, phys_t size, unsigned long flags);
-extern void __iounmap(volatile void __iomem *addr);
+extern void __iounmap(const volatile void __iomem *addr);
 
 static inline void __iomem * __ioremap_mode(phys_t offset, unsigned long size,
 	unsigned long flags)
@@ -279,7 +279,7 @@
 #define ioremap_uncached_accelerated(offset, size)			\
 	__ioremap_mode((offset), (size), _CACHE_UNCACHED_ACCELERATED)
 
-static inline void iounmap(volatile void __iomem *addr)
+static inline void iounmap(const volatile void __iomem *addr)
 {
 #define __IS_KSEG1(addr) (((unsigned long)(addr) & ~0x1fffffffUL) == CKSEG1)