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
  25 static 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
  44 static 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
  59 static 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
  92 static 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  */
 118 extern unsigned long __cmpxchg_called_with_bad_pointer(void)
 119         __compiletime_error("Bad argument size for cmpxchg");
 120
 121 static 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  */
 147 extern unsigned long __xchg_called_with_bad_pointer(void)
 148         __compiletime_error("Bad argument size for xchg");
 149
 150 static 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 */