arch/hexagon/include/asm/cmpxchg.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * xchg/cmpxchg operations for the Hexagon architecture
   4  *
   5  * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   6  */
   7
   8 #ifndef _ASM_CMPXCHG_H
   9 #define _ASM_CMPXCHG_H
  10
  11 /*
  12  * __xchg - atomically exchange a register and a memory location
  13  * @x: value to swap
  14  * @ptr: pointer to memory
  15  * @size:  size of the value
  16  *
  17  * Only 4 bytes supported currently.
  18  *
  19  * Note:  there was an errata for V2 about .new's and memw_locked.
  20  *
  21  */
  22 static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
  23                                    int size)
  24 {
  25         unsigned long retval;
  26
  27         /*  Can't seem to use printk or panic here, so just stop  */
  28         if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
  29
  30         __asm__ __volatile__ (
  31         "1:     %0 = memw_locked(%1);\n"    /*  load into retval */
  32         "       memw_locked(%1,P0) = %2;\n" /*  store into memory */
  33         "       if (!P0) jump 1b;\n"
  34         : "=&r" (retval)
  35         : "r" (ptr), "r" (x)
  36         : "memory", "p0"
  37         );
  38         return retval;
  39 }
  40
  41 /*
  42  * Atomically swap the contents of a register with memory.  Should be atomic
  43  * between multiple CPU's and within interrupts on the same CPU.
  44  */
  45 #define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
  46         sizeof(*(ptr))))
  47
  48 /*
  49  *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
  50  *  looks just like atomic_cmpxchg on our arch currently with a bunch of
  51  *  variable casting.
  52  */
  53
  54 #define cmpxchg(ptr, old, new)                                  \
  55 ({                                                              \
  56         __typeof__(ptr) __ptr = (ptr);                          \
  57         __typeof__(*(ptr)) __old = (old);                       \
  58         __typeof__(*(ptr)) __new = (new);                       \
  59         __typeof__(*(ptr)) __oldval = 0;                        \
  60                                                                 \
  61         asm volatile(                                           \
  62                 "1:     %0 = memw_locked(%1);\n"                \
  63                 "       { P0 = cmp.eq(%0,%2);\n"                \
  64                 "         if (!P0.new) jump:nt 2f; }\n"         \
  65                 "       memw_locked(%1,p0) = %3;\n"             \
  66                 "       if (!P0) jump 1b;\n"                    \
  67                 "2:\n"                                          \
  68                 : "=&r" (__oldval)                              \
  69                 : "r" (__ptr), "r" (__old), "r" (__new)         \
  70                 : "memory", "p0"                                \
  71         );                                                      \
  72         __oldval;                                               \
  73 })
  74
  75 #endif /* _ASM_CMPXCHG_H */