[MIPS] MIPS64 R2 optimizations for 64-bit endianess swapping.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/byteorder.h

@@ -39,6 +39,24 @@ static __inline__ __attribute_const__ __u32 ___arch__swab32(__u32 x)
 }
 #define __arch__swab32(x)	___arch__swab32(x)
 
+#ifdef CONFIG_CPU_MIPS64_R2
+
+static __inline__ __attribute_const__ __u64 ___arch__swab64(__u64 x)
+{
+	__asm__(
+	"	dsbh	%0, %1			\n"
+	"	dshd	%0, %0			\n"
+	"	drotr	%0, %0, 32		\n"
+	: "=r" (x)
+	: "r" (x));
+
+	return x;
+}
+
+#define __arch__swab64(x)	___arch__swab64(x)
+
+#endif /* CONFIG_CPU_MIPS64_R2 */
+
 #endif /* CONFIG_CPU_MIPSR2 */
 
 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)