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50 lines
1.2 KiB
50 lines
1.2 KiB
/* 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 <[email protected]> |
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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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