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-rw-r--r--arch/sh/include/asm/cmpxchg-xchg.h52
1 files changed, 52 insertions, 0 deletions
diff --git a/arch/sh/include/asm/cmpxchg-xchg.h b/arch/sh/include/asm/cmpxchg-xchg.h
new file mode 100644
index 000000000..593a97047
--- /dev/null
+++ b/arch/sh/include/asm/cmpxchg-xchg.h
@@ -0,0 +1,52 @@
+#ifndef __ASM_SH_CMPXCHG_XCHG_H
+#define __ASM_SH_CMPXCHG_XCHG_H
+
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * 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/bits.h>
+#include <linux/compiler.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) - size - 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 */