1 #ifndef __ASM_SH_CMPXCHG_XCHG_H 2 #define __ASM_SH_CMPXCHG_XCHG_H 3 4 /* 5 * Copyright (C) 2016 Red Hat, Inc. 6 * Author: Michael S. Tsirkin <mst@redhat.com> 7 * 8 * This work is licensed under the terms of the GNU GPL, version 2. See the 9 * file "COPYING" in the main directory of this archive for more details. 10 */ 11 #include <linux/bitops.h> 12 #include <asm/byteorder.h> 13 14 /* 15 * Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg. 16 * Note: this header isn't self-contained: before including it, __cmpxchg_u32 17 * must be defined first. 18 */ 19 static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size) 20 { 21 int off = (unsigned long)ptr % sizeof(u32); 22 volatile u32 *p = ptr - off; 23 #ifdef __BIG_ENDIAN 24 int bitoff = (sizeof(u32) - 1 - off) * BITS_PER_BYTE; 25 #else 26 int bitoff = off * BITS_PER_BYTE; 27 #endif 28 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 29 u32 oldv, newv; 30 u32 ret; 31 32 do { 33 oldv = READ_ONCE(*p); 34 ret = (oldv & bitmask) >> bitoff; 35 newv = (oldv & ~bitmask) | (x << bitoff); 36 } while (__cmpxchg_u32(p, oldv, newv) != oldv); 37 38 return ret; 39 } 40 41 static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val) 42 { 43 return __xchg_cmpxchg(m, val, sizeof *m); 44 } 45 46 static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val) 47 { 48 return __xchg_cmpxchg(m, val, sizeof *m); 49 } 50 51 #endif /* __ASM_SH_CMPXCHG_XCHG_H */ 52