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/bits.h> 12 #include <linux/compiler.h> 13 #include <asm/byteorder.h> 14 15 /* 16 * Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg. 17 * Note: this header isn't self-contained: before including it, __cmpxchg_u32 18 * must be defined first. 19 */ 20 static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size) 21 { 22 int off = (unsigned long)ptr % sizeof(u32); 23 volatile u32 *p = ptr - off; 24 #ifdef __BIG_ENDIAN 25 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; 26 #else 27 int bitoff = off * BITS_PER_BYTE; 28 #endif 29 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 30 u32 oldv, newv; 31 u32 ret; 32 33 do { 34 oldv = READ_ONCE(*p); 35 ret = (oldv & bitmask) >> bitoff; 36 newv = (oldv & ~bitmask) | (x << bitoff); 37 } while (__cmpxchg_u32(p, oldv, newv) != oldv); 38 39 return ret; 40 } 41 42 static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val) 43 { 44 return __xchg_cmpxchg(m, val, sizeof *m); 45 } 46 47 static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val) 48 { 49 return __xchg_cmpxchg(m, val, sizeof *m); 50 } 51 52 #endif /* __ASM_SH_CMPXCHG_XCHG_H */ 53