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Commit 9e3f84ce authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

sh: move xchg_cmpxchg to a header by itself 



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: default avatarRich Felker <dalias@libc.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 3226aad8

arch/sh/include/asm/cmpxchg-llsc.h

+1 −34
Original line number Diff line number Diff line 
#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 */

arch/sh/include/asm/cmpxchg-xchg.h

0 → 100644
+51 −0
Original line number Diff line number Diff line 
#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/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 */