arch/mips/include/asm/cmpxchg.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2003, 06, 07 by Ralf Baechle (ralf@linux-mips.org)
   7  */
   8 #ifndef __ASM_CMPXCHG_H
   9 #define __ASM_CMPXCHG_H
  10
  11 #include <linux/bug.h>
  12 #include <linux/irqflags.h>
  13 #include <asm/compiler.h>
  14 #include <asm/war.h>
  15
  16 /*
  17  * Using a branch-likely instruction to check the result of an sc instruction
  18  * works around a bug present in R10000 CPUs prior to revision 3.0 that could
  19  * cause ll-sc sequences to execute non-atomically.
  20  */
  21 #if R10000_LLSC_WAR
  22 # define __scbeqz "beqzl"
  23 #else
  24 # define __scbeqz "beqz"
  25 #endif
  26
  27 /*
  28  * These functions doesn't exist, so if they are called you'll either:
  29  *
  30  * - Get an error at compile-time due to __compiletime_error, if supported by
  31  *   your compiler.
  32  *
  33  * or:
  34  *
  35  * - Get an error at link-time due to the call to the missing function.
  36  */
  37 extern unsigned long __cmpxchg_called_with_bad_pointer(void)
  38         __compiletime_error("Bad argument size for cmpxchg");
  39 extern unsigned long __xchg_called_with_bad_pointer(void)
  40         __compiletime_error("Bad argument size for xchg");
  41
  42 #define __xchg_asm(ld, st, m, val)                                      \
  43 ({                                                                      \
  44         __typeof(*(m)) __ret;                                           \
  45                                                                         \
  46         if (kernel_uses_llsc) {                                         \
  47                 __asm__ __volatile__(                                   \
  48                 "       .set    push                            \n"     \
  49                 "       .set    noat                            \n"     \
  50                 "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
  51                 "1:     " ld "  %0, %2          # __xchg_asm    \n"     \
  52                 "       .set    mips0                           \n"     \
  53                 "       move    $1, %z3                         \n"     \
  54                 "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
  55                 "       " st "  $1, %1                          \n"     \
  56                 "\t" __scbeqz " $1, 1b                          \n"     \
  57                 "       .set    pop                             \n"     \
  58                 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
  59                 : GCC_OFF_SMALL_ASM() (*m), "Jr" (val)                  \
  60                 : "memory");                                            \
  61         } else {                                                        \
  62                 unsigned long __flags;                                  \
  63                                                                         \
  64                 raw_local_irq_save(__flags);                            \
  65                 __ret = *m;                                             \
  66                 *m = val;                                               \
  67                 raw_local_irq_restore(__flags);                         \
  68         }                                                               \
  69                                                                         \
  70         __ret;                                                          \
  71 })
  72
  73 extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
  74                                   unsigned int size);
  75
  76 static inline unsigned long __xchg(volatile void *ptr, unsigned long x,
  77                                    int size)
  78 {
  79         switch (size) {
  80         case 1:
  81         case 2:
  82                 return __xchg_small(ptr, x, size);
  83
  84         case 4:
  85                 return __xchg_asm("ll", "sc", (volatile u32 *)ptr, x);
  86
  87         case 8:
  88                 if (!IS_ENABLED(CONFIG_64BIT))
  89                         return __xchg_called_with_bad_pointer();
  90
  91                 return __xchg_asm("lld", "scd", (volatile u64 *)ptr, x);
  92
  93         default:
  94                 return __xchg_called_with_bad_pointer();
  95         }
  96 }
  97
  98 #define xchg(ptr, x)                                                    \
  99 ({                                                                      \
 100         __typeof__(*(ptr)) __res;                                       \
 101                                                                         \
 102         smp_mb__before_llsc();                                          \
 103                                                                         \
 104         __res = (__typeof__(*(ptr)))                                    \
 105                 __xchg((ptr), (unsigned long)(x), sizeof(*(ptr)));      \
 106                                                                         \
 107         smp_llsc_mb();                                                  \
 108                                                                         \
 109         __res;                                                          \
 110 })
 111
 112 #define __cmpxchg_asm(ld, st, m, old, new)                              \
 113 ({                                                                      \
 114         __typeof(*(m)) __ret;                                           \
 115                                                                         \
 116         if (kernel_uses_llsc) {                                         \
 117                 __asm__ __volatile__(                                   \
 118                 "       .set    push                            \n"     \
 119                 "       .set    noat                            \n"     \
 120                 "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
 121                 "1:     " ld "  %0, %2          # __cmpxchg_asm \n"     \
 122                 "       bne     %0, %z3, 2f                     \n"     \
 123                 "       .set    mips0                           \n"     \
 124                 "       move    $1, %z4                         \n"     \
 125                 "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
 126                 "       " st "  $1, %1                          \n"     \
 127                 "\t" __scbeqz " $1, 1b                          \n"     \
 128                 "       .set    pop                             \n"     \
 129                 "2:                                             \n"     \
 130                 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
 131                 : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new)              \
 132                 : "memory");                                            \
 133         } else {                                                        \
 134                 unsigned long __flags;                                  \
 135                                                                         \
 136                 raw_local_irq_save(__flags);                            \
 137                 __ret = *m;                                             \
 138                 if (__ret == old)                                       \
 139                         *m = new;                                       \
 140                 raw_local_irq_restore(__flags);                         \
 141         }                                                               \
 142                                                                         \
 143         __ret;                                                          \
 144 })
 145
 146 extern unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
 147                                      unsigned long new, unsigned int size);
 148
 149 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 150                                       unsigned long new, unsigned int size)
 151 {
 152         switch (size) {
 153         case 1:
 154         case 2:
 155                 return __cmpxchg_small(ptr, old, new, size);
 156
 157         case 4:
 158                 return __cmpxchg_asm("ll", "sc", (volatile u32 *)ptr,
 159                                      (u32)old, new);
 160
 161         case 8:
 162                 /* lld/scd are only available for MIPS64 */
 163                 if (!IS_ENABLED(CONFIG_64BIT))
 164                         return __cmpxchg_called_with_bad_pointer();
 165
 166                 return __cmpxchg_asm("lld", "scd", (volatile u64 *)ptr,
 167                                      (u64)old, new);
 168
 169         default:
 170                 return __cmpxchg_called_with_bad_pointer();
 171         }
 172 }
 173
 174 #define cmpxchg_local(ptr, old, new)                                    \
 175         ((__typeof__(*(ptr)))                                           \
 176                 __cmpxchg((ptr),                                        \
 177                           (unsigned long)(__typeof__(*(ptr)))(old),     \
 178                           (unsigned long)(__typeof__(*(ptr)))(new),     \
 179                           sizeof(*(ptr))))
 180
 181 #define cmpxchg(ptr, old, new)                                          \
 182 ({                                                                      \
 183         __typeof__(*(ptr)) __res;                                       \
 184                                                                         \
 185         smp_mb__before_llsc();                                          \
 186         __res = cmpxchg_local((ptr), (old), (new));                     \
 187         smp_llsc_mb();                                                  \
 188                                                                         \
 189         __res;                                                          \
 190 })
 191
 192 #ifdef CONFIG_64BIT
 193 #define cmpxchg64_local(ptr, o, n)                                      \
 194   ({                                                                    \
 195         BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
 196         cmpxchg_local((ptr), (o), (n));                                 \
 197   })
 198
 199 #define cmpxchg64(ptr, o, n)                                            \
 200   ({                                                                    \
 201         BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
 202         cmpxchg((ptr), (o), (n));                                       \
 203   })
 204 #else
 205 #include <asm-generic/cmpxchg-local.h>
 206 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 207 #ifndef CONFIG_SMP
 208 #define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
 209 #endif
 210 #endif
 211
 212 #undef __scbeqz
 213
 214 #endif /* __ASM_CMPXCHG_H */