LXR linux/arch/openrisc/include/asm/cmpxchg.h

   1/*
   2 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
   3 *
   4 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
   5 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
   6 *
   7 * This file is licensed under the terms of the GNU General Public License
   8 * version 2.  This program is licensed "as is" without any warranty of any
   9 * kind, whether express or implied.
  10 *
  11 * Note:
  12 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4
  13 * byte cmpxchg is sourced heavily from the sh and mips implementations.
  14 */
  15
  16#ifndef __ASM_OPENRISC_CMPXCHG_H
  17#define __ASM_OPENRISC_CMPXCHG_H
  18
  19#include  <linux/bits.h>
  20#include  <linux/compiler.h>
  21#include  <linux/types.h>
  22
  23#define __HAVE_ARCH_CMPXCHG 1
  24
  25static inline unsigned long cmpxchg_u32(volatile void *ptr,
  26                unsigned long old, unsigned long new)
  27{
  28        __asm__ __volatile__(
  29                "1:     l.lwa %0, 0(%1)         \n"
  30                "       l.sfeq %0, %2           \n"
  31                "       l.bnf 2f                \n"
  32                "        l.nop                  \n"
  33                "       l.swa 0(%1), %3         \n"
  34                "       l.bnf 1b                \n"
  35                "        l.nop                  \n"
  36                "2:                             \n"
  37                : "=&r"(old)
  38                : "r"(ptr), "r"(old), "r"(new)
  39                : "cc", "memory");
  40
  41        return old;
  42}
  43
  44static inline unsigned long xchg_u32(volatile void *ptr,
  45                unsigned long val)
  46{
  47        __asm__ __volatile__(
  48                "1:     l.lwa %0, 0(%1)         \n"
  49                "       l.swa 0(%1), %2         \n"
  50                "       l.bnf 1b                \n"
  51                "        l.nop                  \n"
  52                : "=&r"(val)
  53                : "r"(ptr), "r"(val)
  54                : "cc", "memory");
  55
  56        return val;
  57}
  58
  59static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
  60                                int size)
  61{
  62        int off = (unsigned long)ptr % sizeof(u32);
  63        volatile u32 *p = ptr - off;
  64#ifdef __BIG_ENDIAN
  65        int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
  66#else
  67        int bitoff = off * BITS_PER_BYTE;
  68#endif
  69        u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
  70        u32 load32, old32, new32;
  71        u32 ret;
  72
  73        load32 = READ_ONCE(*p);
  74
  75        while (true) {
  76                ret = (load32 & bitmask) >> bitoff;
  77                if (old != ret)
  78                        return ret;
  79
  80                old32 = (load32 & ~bitmask) | (old << bitoff);
  81                new32 = (load32 & ~bitmask) | (new << bitoff);
  82
  83                /* Do 32 bit cmpxchg */
  84                load32 = cmpxchg_u32(p, old32, new32);
  85                if (load32 == old32)
  86                        return old;
  87        }
  88}
  89
  90/* xchg */
  91
  92static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
  93{
  94        int off = (unsigned long)ptr % sizeof(u32);
  95        volatile u32 *p = ptr - off;
  96#ifdef __BIG_ENDIAN
  97        int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
  98#else
  99        int bitoff = off * BITS_PER_BYTE;
 100#endif
 101        u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
 102        u32 oldv, newv;
 103        u32 ret;
 104
 105        do {
 106                oldv = READ_ONCE(*p);
 107                ret = (oldv & bitmask) >> bitoff;
 108                newv = (oldv & ~bitmask) | (x << bitoff);
 109        } while (cmpxchg_u32(p, oldv, newv) != oldv);
 110
 111        return ret;
 112}
 113
 114/*
 115 * This function doesn't exist, so you'll get a linker error
 116 * if something tries to do an invalid cmpxchg().
 117 */
 118extern unsigned long __cmpxchg_called_with_bad_pointer(void)
 119        __compiletime_error("Bad argument size for cmpxchg");
 120
 121static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 122                unsigned long new, int size)
 123{
 124        switch (size) {
 125        case 1:
 126        case 2:
 127                return cmpxchg_small(ptr, old, new, size);
 128        case 4:
 129                return cmpxchg_u32(ptr, old, new);
 130        default:
 131                return __cmpxchg_called_with_bad_pointer();
 132        }
 133}
 134
 135#define arch_cmpxchg(ptr, o, n)                                         \
 136        ({                                                              \
 137                (__typeof__(*(ptr))) __cmpxchg((ptr),                   \
 138                                               (unsigned long)(o),      \
 139                                               (unsigned long)(n),      \
 140                                               sizeof(*(ptr)));         \
 141        })
 142
 143/*
 144 * This function doesn't exist, so you'll get a linker error if
 145 * something tries to do an invalidly-sized xchg().
 146 */
 147extern unsigned long __xchg_called_with_bad_pointer(void)
 148        __compiletime_error("Bad argument size for xchg");
 149
 150static inline unsigned long __xchg(volatile void *ptr, unsigned long with,
 151                int size)
 152{
 153        switch (size) {
 154        case 1:
 155        case 2:
 156                return xchg_small(ptr, with, size);
 157        case 4:
 158                return xchg_u32(ptr, with);
 159        default:
 160                return __xchg_called_with_bad_pointer();
 161        }
 162}
 163
 164#define arch_xchg(ptr, with)                                            \
 165        ({                                                              \
 166                (__typeof__(*(ptr))) __xchg((ptr),                      \
 167                                            (unsigned long)(with),      \
 168                                            sizeof(*(ptr)));            \
 169        })
 170
 171#endif /* __ASM_OPENRISC_CMPXCHG_H */
 172