1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __ASM_SH_CMPXCHG_XCHG_H 3 #define __ASM_SH_CMPXCHG_XCHG_H 4 5 /* 6 * Copyright (C) 2016 Red Hat, Inc. 7 * Author: Michael S. Tsirkin <mst@redhat.com> 8 */ 9 #include <linux/bits.h> 10 #include <linux/compiler.h> 11 #include <asm/byteorder.h> 12 13 /* 14 * Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg. 15 * Note: this header isn't self-contained: before including it, __cmpxchg_u32 16 * must be defined first. 17 */ 18 static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size) 19 { 20 int off = (unsigned long)ptr % sizeof(u32); 21 volatile u32 *p = ptr - off; 22 #ifdef __BIG_ENDIAN 23 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; 24 #else 25 int bitoff = off * BITS_PER_BYTE; 26 #endif 27 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 28 u32 oldv, newv; 29 u32 ret; 30 31 do { 32 oldv = READ_ONCE(*p); 33 ret = (oldv & bitmask) >> bitoff; 34 newv = (oldv & ~bitmask) | (x << bitoff); 35 } while (__cmpxchg_u32(p, oldv, newv) != oldv); 36 37 return ret; 38 } 39 40 static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val) 41 { 42 return __xchg_cmpxchg(m, val, sizeof *m); 43 } 44 45 static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val) 46 { 47 return __xchg_cmpxchg(m, val, sizeof *m); 48 } 49 50 #endif /* __ASM_SH_CMPXCHG_XCHG_H */ 51