51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_SH_CMPXCHG_XCHG_H
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#define __ASM_SH_CMPXCHG_XCHG_H
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/*
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* Copyright (C) 2016 Red Hat, Inc.
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* Author: Michael S. Tsirkin <mst@redhat.com>
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*/
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#include <linux/bits.h>
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#include <linux/compiler.h>
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#include <asm/byteorder.h>
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/*
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* Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg.
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* Note: this header isn't self-contained: before including it, __cmpxchg_u32
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* must be defined first.
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*/
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static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
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{
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int off = (unsigned long)ptr % sizeof(u32);
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volatile u32 *p = ptr - off;
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#ifdef __BIG_ENDIAN
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int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
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#else
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int bitoff = off * BITS_PER_BYTE;
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#endif
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u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
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u32 oldv, newv;
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u32 ret;
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do {
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oldv = READ_ONCE(*p);
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ret = (oldv & bitmask) >> bitoff;
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newv = (oldv & ~bitmask) | (x << bitoff);
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} while (__cmpxchg_u32(p, oldv, newv) != oldv);
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return ret;
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}
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static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
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{
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return __xchg_cmpxchg(m, val, sizeof *m);
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}
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static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
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{
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return __xchg_cmpxchg(m, val, sizeof *m);
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}
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#endif /* __ASM_SH_CMPXCHG_XCHG_H */
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