Looks like future sh variants will support a 4-byte cas which will be
used to implement 1 and 2 byte xchg.
This is exactly what we do for llsc now, move the portable part of the
code into a separate header so it's easy to reuse.
Suggested-by: Rich Felker <dalias@xxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
arch/sh/include/asm/cmpxchg-llsc.h | 35 +-------------------------
arch/sh/include/asm/cmpxchg-xchg.h | 51 ++++++++++++++++++++++++++++++++++++++
2 files changed, 52 insertions(+), 34 deletions(-)
create mode 100644 arch/sh/include/asm/cmpxchg-xchg.h
diff --git a/arch/sh/include/asm/cmpxchg-llsc.h b/arch/sh/include/asm/cmpxchg-llsc.h
index e754794..fcfd322 100644
--- a/arch/sh/include/asm/cmpxchg-llsc.h
+++ b/arch/sh/include/asm/cmpxchg-llsc.h
@@ -1,9 +1,6 @@
#ifndef __ASM_SH_CMPXCHG_LLSC_H
#define __ASM_SH_CMPXCHG_LLSC_H
-#include <linux/bitops.h>
-#include <asm/byteorder.h>
-
static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val)
{
unsigned long retval;
@@ -50,36 +47,6 @@ __cmpxchg_u32(volatile u32 *m, unsigned long old, unsigned long new)
return retval;
}
-static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
-{
- int off = (unsigned long)ptr % sizeof(u32);
- volatile u32 *p = ptr - off;
-#ifdef __BIG_ENDIAN
- int bitoff = (sizeof(u32) - 1 - off) * BITS_PER_BYTE;
-#else
- int bitoff = off * BITS_PER_BYTE;
-#endif
- u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
- u32 oldv, newv;
- u32 ret;
-
- do {
- oldv = READ_ONCE(*p);
- ret = (oldv & bitmask) >> bitoff;
- newv = (oldv & ~bitmask) | (x << bitoff);
- } while (__cmpxchg_u32(p, oldv, newv) != oldv);
-
- return ret;
-}
-
-static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
-{
- return __xchg_cmpxchg(m, val, sizeof *m);
-}
-
-static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
-{
- return __xchg_cmpxchg(m, val, sizeof *m);
-}
+#include <asm/cmpxchg-xchg.h>
#endif /* __ASM_SH_CMPXCHG_LLSC_H */
diff --git a/arch/sh/include/asm/cmpxchg-xchg.h b/arch/sh/include/asm/cmpxchg-xchg.h
new file mode 100644
index 0000000..7219719
--- /dev/null
+++ b/arch/sh/include/asm/cmpxchg-xchg.h
@@ -0,0 +1,51 @@
+#ifndef __ASM_SH_CMPXCHG_XCHG_H
+#define __ASM_SH_CMPXCHG_XCHG_H
+
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@xxxxxxxxxx>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See the
+ * file "COPYING" in the main directory of this archive for more details.
+ */
+#include <linux/bitops.h>
+#include <asm/byteorder.h>
+
+/*
+ * Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg.
+ * Note: this header isn't self-contained: before including it, __cmpxchg_u32
+ * must be defined first.
+ */
+static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
+{
+ int off = (unsigned long)ptr % sizeof(u32);
+ volatile u32 *p = ptr - off;
+#ifdef __BIG_ENDIAN
+ int bitoff = (sizeof(u32) - 1 - off) * BITS_PER_BYTE;
+#else
+ int bitoff = off * BITS_PER_BYTE;
+#endif
+ u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
+ u32 oldv, newv;
+ u32 ret;
+
+ do {
+ oldv = READ_ONCE(*p);
+ ret = (oldv & bitmask) >> bitoff;
+ newv = (oldv & ~bitmask) | (x << bitoff);
+ } while (__cmpxchg_u32(p, oldv, newv) != oldv);
+
+ return ret;
+}
+
+static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
+{
+ return __xchg_cmpxchg(m, val, sizeof *m);
+}
+
+static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
+{
+ return __xchg_cmpxchg(m, val, sizeof *m);
+}
+
+#endif /* __ASM_SH_CMPXCHG_XCHG_H */
--
MST
