diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
index 72f7929736f8..94ef71b38b69 100644
--- a/arch/arc/include/asm/io.h
+++ b/arch/arc/include/asm/io.h
@@ -32,7 +32,7 @@ static inline void ioport_unmap(void __iomem *addr)
 {
 }
 
-extern void iounmap(const void __iomem *addr);
+extern void iounmap(const volatile void __iomem *addr);
 
 #define ioremap_nocache(phy, sz)	ioremap(phy, sz)
 #define ioremap_wc(phy, sz)		ioremap(phy, sz)
diff --git a/arch/arc/mm/ioremap.c b/arch/arc/mm/ioremap.c
index 95c649fbc95a..d3b1ea16e9cd 100644
--- a/arch/arc/mm/ioremap.c
+++ b/arch/arc/mm/ioremap.c
@@ -93,7 +93,7 @@ void __iomem *ioremap_prot(phys_addr_t paddr, unsigned long size,
 EXPORT_SYMBOL(ioremap_prot);
 
 
-void iounmap(const void __iomem *addr)
+void iounmap(const volatile void __iomem *addr)
 {
 	/* weird double cast to handle phys_addr_t > 32 bits */
 	if (arc_uncached_addr_space((phys_addr_t)(u32)addr))