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/llsc.h>
  15 #include <asm/sync.h>
  16 #include <asm/war.h>
  17
  18 /*
  19  * These functions doesn't exist, so if they are called you'll either:
  20  *
  21  * - Get an error at compile-time due to __compiletime_error, if supported by
  22  *   your compiler.
  23  *
  24  * or:
  25  *
  26  * - Get an error at link-time due to the call to the missing function.
  27  */
  28 extern unsigned long __cmpxchg_called_with_bad_pointer(void)
  29         __compiletime_error("Bad argument size for cmpxchg");
  30 extern unsigned long __cmpxchg64_unsupported(void)
  31         __compiletime_error("cmpxchg64 not available; cpu_has_64bits may be false");
  32 extern unsigned long __xchg_called_with_bad_pointer(void)
  33         __compiletime_error("Bad argument size for xchg");
  34
  35 #define __xchg_asm(ld, st, m, val)                                      \
  36 ({                                                                      \
  37         __typeof(*(m)) __ret;                                           \
  38                                                                         \
  39         if (kernel_uses_llsc) {                                         \
  40                 __asm__ __volatile__(                                   \
  41                 "       .set    push                            \n"     \
  42                 "       .set    noat                            \n"     \
  43                 "       .set    push                            \n"     \
  44                 "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
  45                 "       " __SYNC(full, loongson3_war) "         \n"     \
  46                 "1:     " ld "  %0, %2          # __xchg_asm    \n"     \
  47                 "       .set    pop                             \n"     \
  48                 "       move    $1, %z3                         \n"     \
  49                 "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
  50                 "       " st "  $1, %1                          \n"     \
  51                 "\t" __SC_BEQZ  "$1, 1b                         \n"     \
  52                 "       .set    pop                             \n"     \
  53                 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
  54                 : GCC_OFF_SMALL_ASM() (*m), "Jr" (val)                  \
  55                 : __LLSC_CLOBBER);                                      \
  56         } else {                                                        \
  57                 unsigned long __flags;                                  \
  58                                                                         \
  59                 raw_local_irq_save(__flags);                            \
  60                 __ret = *m;                                             \
  61                 *m = val;                                               \
  62                 raw_local_irq_restore(__flags);                         \
  63         }                                                               \
  64                                                                         \
  65         __ret;                                                          \
  66 })
  67
  68 extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
  69                                   unsigned int size);
  70
  71 static __always_inline
  72 unsigned long __xchg(volatile void *ptr, unsigned long x, int size)
  73 {
  74         switch (size) {
  75         case 1:
  76         case 2:
  77                 return __xchg_small(ptr, x, size);
  78
  79         case 4:
  80                 return __xchg_asm("ll", "sc", (volatile u32 *)ptr, x);
  81
  82         case 8:
  83                 if (!IS_ENABLED(CONFIG_64BIT))
  84                         return __xchg_called_with_bad_pointer();
  85
  86                 return __xchg_asm("lld", "scd", (volatile u64 *)ptr, x);
  87
  88         default:
  89                 return __xchg_called_with_bad_pointer();
  90         }
  91 }
  92
  93 #define xchg(ptr, x)                                                    \
  94 ({                                                                      \
  95         __typeof__(*(ptr)) __res;                                       \
  96                                                                         \
  97         /*                                                              \
  98          * In the Loongson3 workaround case __xchg_asm() already        \
  99          * contains a completion barrier prior to the LL, so we don't   \
 100          * need to emit an extra one here.                              \
 101          */                                                             \
 102         if (!__SYNC_loongson3_war)                                      \
 103                 smp_mb__before_llsc();                                  \
 104                                                                         \
 105         __res = (__typeof__(*(ptr)))                                    \
 106                 __xchg((ptr), (unsigned long)(x), sizeof(*(ptr)));      \
 107                                                                         \
 108         smp_llsc_mb();                                                  \
 109                                                                         \
 110         __res;                                                          \
 111 })
 112
 113 #define __cmpxchg_asm(ld, st, m, old, new)                              \
 114 ({                                                                      \
 115         __typeof(*(m)) __ret;                                           \
 116                                                                         \
 117         if (kernel_uses_llsc) {                                         \
 118                 __asm__ __volatile__(                                   \
 119                 "       .set    push                            \n"     \
 120                 "       .set    noat                            \n"     \
 121                 "       .set    push                            \n"     \
 122                 "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
 123                 "       " __SYNC(full, loongson3_war) "         \n"     \
 124                 "1:     " ld "  %0, %2          # __cmpxchg_asm \n"     \
 125                 "       bne     %0, %z3, 2f                     \n"     \
 126                 "       .set    pop                             \n"     \
 127                 "       move    $1, %z4                         \n"     \
 128                 "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
 129                 "       " st "  $1, %1                          \n"     \
 130                 "\t" __SC_BEQZ  "$1, 1b                         \n"     \
 131                 "       .set    pop                             \n"     \
 132                 "2:     " __SYNC(full, loongson3_war) "         \n"     \
 133                 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
 134                 : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new)      \
 135                 : __LLSC_CLOBBER);                                      \
 136         } else {                                                        \
 137                 unsigned long __flags;                                  \
 138                                                                         \
 139                 raw_local_irq_save(__flags);                            \
 140                 __ret = *m;                                             \
 141                 if (__ret == old)                                       \
 142                         *m = new;                                       \
 143                 raw_local_irq_restore(__flags);                         \
 144         }                                                               \
 145                                                                         \
 146         __ret;                                                          \
 147 })
 148
 149 extern unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
 150                                      unsigned long new, unsigned int size);
 151
 152 static __always_inline
 153 unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 154                         unsigned long new, unsigned int size)
 155 {
 156         switch (size) {
 157         case 1:
 158         case 2:
 159                 return __cmpxchg_small(ptr, old, new, size);
 160
 161         case 4:
 162                 return __cmpxchg_asm("ll", "sc", (volatile u32 *)ptr,
 163                                      (u32)old, new);
 164
 165         case 8:
 166                 /* lld/scd are only available for MIPS64 */
 167                 if (!IS_ENABLED(CONFIG_64BIT))
 168                         return __cmpxchg_called_with_bad_pointer();
 169
 170                 return __cmpxchg_asm("lld", "scd", (volatile u64 *)ptr,
 171                                      (u64)old, new);
 172
 173         default:
 174                 return __cmpxchg_called_with_bad_pointer();
 175         }
 176 }
 177
 178 #define cmpxchg_local(ptr, old, new)                                    \
 179         ((__typeof__(*(ptr)))                                           \
 180                 __cmpxchg((ptr),                                        \
 181                           (unsigned long)(__typeof__(*(ptr)))(old),     \
 182                           (unsigned long)(__typeof__(*(ptr)))(new),     \
 183                           sizeof(*(ptr))))
 184
 185 #define cmpxchg(ptr, old, new)                                          \
 186 ({                                                                      \
 187         __typeof__(*(ptr)) __res;                                       \
 188                                                                         \
 189         /*                                                              \
 190          * In the Loongson3 workaround case __cmpxchg_asm() already     \
 191          * contains a completion barrier prior to the LL, so we don't   \
 192          * need to emit an extra one here.                              \
 193          */                                                             \
 194         if (!__SYNC_loongson3_war)                                      \
 195                 smp_mb__before_llsc();                                  \
 196                                                                         \
 197         __res = cmpxchg_local((ptr), (old), (new));                     \
 198                                                                         \
 199         /*                                                              \
 200          * In the Loongson3 workaround case __cmpxchg_asm() already     \
 201          * contains a completion barrier after the SC, so we don't      \
 202          * need to emit an extra one here.                              \
 203          */                                                             \
 204         if (!__SYNC_loongson3_war)                                      \
 205                 smp_llsc_mb();                                          \
 206                                                                         \
 207         __res;                                                          \
 208 })
 209
 210 #ifdef CONFIG_64BIT
 211 #define cmpxchg64_local(ptr, o, n)                                      \
 212   ({                                                                    \
 213         BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
 214         cmpxchg_local((ptr), (o), (n));                                 \
 215   })
 216
 217 #define cmpxchg64(ptr, o, n)                                            \
 218   ({                                                                    \
 219         BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
 220         cmpxchg((ptr), (o), (n));                                       \
 221   })
 222 #else
 223
 224 # include <asm-generic/cmpxchg-local.h>
 225 # define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 226
 227 # ifdef CONFIG_SMP
 228
 229 static inline unsigned long __cmpxchg64(volatile void *ptr,
 230                                         unsigned long long old,
 231                                         unsigned long long new)
 232 {
 233         unsigned long long tmp, ret;
 234         unsigned long flags;
 235
 236         /*
 237          * The assembly below has to combine 32 bit values into a 64 bit
 238          * register, and split 64 bit values from one register into two. If we
 239          * were to take an interrupt in the middle of this we'd only save the
 240          * least significant 32 bits of each register & probably clobber the
 241          * most significant 32 bits of the 64 bit values we're using. In order
 242          * to avoid this we must disable interrupts.
 243          */
 244         local_irq_save(flags);
 245
 246         asm volatile(
 247         "       .set    push                            \n"
 248         "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"
 249         /* Load 64 bits from ptr */
 250         "       " __SYNC(full, loongson3_war) "         \n"
 251         "1:     lld     %L0, %3         # __cmpxchg64   \n"
 252         /*
 253          * Split the 64 bit value we loaded into the 2 registers that hold the
 254          * ret variable.
 255          */
 256         "       dsra    %M0, %L0, 32                    \n"
 257         "       sll     %L0, %L0, 0                     \n"
 258         /*
 259          * Compare ret against old, breaking out of the loop if they don't
 260          * match.
 261          */
 262         "       bne     %M0, %M4, 2f                    \n"
 263         "       bne     %L0, %L4, 2f                    \n"
 264         /*
 265          * Combine the 32 bit halves from the 2 registers that hold the new
 266          * variable into a single 64 bit register.
 267          */
 268 #  if MIPS_ISA_REV >= 2
 269         "       move    %L1, %L5                        \n"
 270         "       dins    %L1, %M5, 32, 32                \n"
 271 #  else
 272         "       dsll    %L1, %L5, 32                    \n"
 273         "       dsrl    %L1, %L1, 32                    \n"
 274         "       .set    noat                            \n"
 275         "       dsll    $at, %M5, 32                    \n"
 276         "       or      %L1, %L1, $at                   \n"
 277         "       .set    at                              \n"
 278 #  endif
 279         /* Attempt to store new at ptr */
 280         "       scd     %L1, %2                         \n"
 281         /* If we failed, loop! */
 282         "\t" __SC_BEQZ "%L1, 1b                         \n"
 283         "       .set    pop                             \n"
 284         "2:     " __SYNC(full, loongson3_war) "         \n"
 285         : "=&r"(ret),
 286           "=&r"(tmp),
 287           "=" GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr)
 288         : GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr),
 289           "r" (old),
 290           "r" (new)
 291         : "memory");
 292
 293         local_irq_restore(flags);
 294         return ret;
 295 }
 296
 297 #  define cmpxchg64(ptr, o, n) ({                                       \
 298         unsigned long long __old = (__typeof__(*(ptr)))(o);             \
 299         unsigned long long __new = (__typeof__(*(ptr)))(n);             \
 300         __typeof__(*(ptr)) __res;                                       \
 301                                                                         \
 302         /*                                                              \
 303          * We can only use cmpxchg64 if we know that the CPU supports   \
 304          * 64-bits, ie. lld & scd. Our call to __cmpxchg64_unsupported  \
 305          * will cause a build error unless cpu_has_64bits is a          \
 306          * compile-time constant 1.                                     \
 307          */                                                             \
 308         if (cpu_has_64bits && kernel_uses_llsc) {                       \
 309                 smp_mb__before_llsc();                                  \
 310                 __res = __cmpxchg64((ptr), __old, __new);               \
 311                 smp_llsc_mb();                                          \
 312         } else {                                                        \
 313                 __res = __cmpxchg64_unsupported();                      \
 314         }                                                               \
 315                                                                         \
 316         __res;                                                          \
 317 })
 318
 319 # else /* !CONFIG_SMP */
 320 #  define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
 321 # endif /* !CONFIG_SMP */
 322 #endif /* !CONFIG_64BIT */
 323
 324 #endif /* __ASM_CMPXCHG_H */