alpha: introduce asm/swab.h

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/alpha/include/asm/swab.h b/arch/alpha/include/asm/swab.h
new file mode 100644
index 00000000000..68e7089e02d
--- /dev/null
+++ b/arch/alpha/include/asm/swab.h
@@ -0,0 +1,42 @@
+#ifndef _ALPHA_SWAB_H
+#define _ALPHA_SWAB_H
+
+#include <asm/types.h>
+#include <linux/compiler.h>
+#include <asm/compiler.h>
+
+#ifdef __GNUC__
+
+static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
+{
+	/*
+	 * Unfortunately, we can't use the 6 instruction sequence
+	 * on ev6 since the latency of the UNPKBW is 3, which is
+	 * pretty hard to hide.  Just in case a future implementation
+	 * has a lower latency, here's the sequence (also by Mike Burrows)
+	 *
+	 * UNPKBW a0, v0       v0: 00AA00BB00CC00DD
+	 * SLL v0, 24, a0      a0: BB00CC00DD000000
+	 * BIS v0, a0, a0      a0: BBAACCBBDDCC00DD
+	 * EXTWL a0, 6, v0     v0: 000000000000BBAA
+	 * ZAP a0, 0xf3, a0    a0: 00000000DDCC0000
+	 * ADDL a0, v0, v0     v0: ssssssssDDCCBBAA
+	 */
+
+	__u64 t0, t1, t2, t3;
+
+	t0 = __kernel_inslh(x, 7);	/* t0 : 0000000000AABBCC */
+	t1 = __kernel_inswl(x, 3);	/* t1 : 000000CCDD000000 */
+	t1 |= t0;			/* t1 : 000000CCDDAABBCC */
+	t2 = t1 >> 16;			/* t2 : 0000000000CCDDAA */
+	t0 = t1 & 0xFF00FF00;		/* t0 : 00000000DD00BB00 */
+	t3 = t2 & 0x00FF00FF;		/* t3 : 0000000000CC00AA */
+	t1 = t0 + t3;			/* t1 : ssssssssDDCCBBAA */
+
+	return t1;
+}
+#define __arch_swab32 __arch_swab32
+
+#endif /* __GNUC__ */
+
+#endif /* _ALPHA_SWAB_H */