ARM: 5772/1: Use REV and REV16 for byte swapping on ARMv6+

ARMv6 introduced the REV and REV16 instructions that reverse bytes in
words and halfwords.  Use them for the arch-specific implementation of
the byte swapping helpers on ARMv6+.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/swab.h

@@ -22,6 +22,24 @@
 #  define __SWAB_64_THRU_32__
 #endif
 
+#if defined(__KERNEL__) && __LINUX_ARM_ARCH__ >= 6
+
+static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
+{
+	__asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x));
+	return x;
+}
+#define __arch_swab16 __arch_swab16
+
+static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
+{
+	__asm__ ("rev %0, %1" : "=r" (x) : "r" (x));
+	return x;
+}
+#define __arch_swab32 __arch_swab32
+
+#else
+
 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
 {
 	__u32 t;
@@ -48,3 +66,4 @@ static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
 
 #endif
 
+#endif