LXR linux/arch/sh/include/asm/cmpxchg-xchg.h

   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 */
  18static 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
  40static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
  41{
  42        return __xchg_cmpxchg(m, val, sizeof *m);
  43}
  44
  45static 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