arch/hexagon/include/asm/cmpxchg.h

   1 /*
   2  * xchg/cmpxchg operations for the Hexagon architecture
   3  *
   4  * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   5  *
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 and
   9  * only version 2 as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19  * 02110-1301, USA.
  20  */
  21
  22 #ifndef _ASM_CMPXCHG_H
  23 #define _ASM_CMPXCHG_H
  24
  25 /*
  26  * __xchg - atomically exchange a register and a memory location
  27  * @x: value to swap
  28  * @ptr: pointer to memory
  29  * @size:  size of the value
  30  *
  31  * Only 4 bytes supported currently.
  32  *
  33  * Note:  there was an errata for V2 about .new's and memw_locked.
  34  *
  35  */
  36 static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
  37                                    int size)
  38 {
  39         unsigned long retval;
  40
  41         /*  Can't seem to use printk or panic here, so just stop  */
  42         if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
  43
  44         __asm__ __volatile__ (
  45         "1:     %0 = memw_locked(%1);\n"    /*  load into retval */
  46         "       memw_locked(%1,P0) = %2;\n" /*  store into memory */
  47         "       if !P0 jump 1b;\n"
  48         : "=&r" (retval)
  49         : "r" (ptr), "r" (x)
  50         : "memory", "p0"
  51         );
  52         return retval;
  53 }
  54
  55 /*
  56  * Atomically swap the contents of a register with memory.  Should be atomic
  57  * between multiple CPU's and within interrupts on the same CPU.
  58  */
  59 #define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
  60         sizeof(*(ptr))))
  61
  62 /*
  63  *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
  64  *  looks just like atomic_cmpxchg on our arch currently with a bunch of
  65  *  variable casting.
  66  */
  67 #define __HAVE_ARCH_CMPXCHG 1
  68
  69 #define cmpxchg(ptr, old, new)                                  \
  70 ({                                                              \
  71         __typeof__(ptr) __ptr = (ptr);                          \
  72         __typeof__(*(ptr)) __old = (old);                       \
  73         __typeof__(*(ptr)) __new = (new);                       \
  74         __typeof__(*(ptr)) __oldval = 0;                        \
  75                                                                 \
  76         asm volatile(                                           \
  77                 "1:     %0 = memw_locked(%1);\n"                \
  78                 "       { P0 = cmp.eq(%0,%2);\n"                \
  79                 "         if (!P0.new) jump:nt 2f; }\n"         \
  80                 "       memw_locked(%1,p0) = %3;\n"             \
  81                 "       if (!P0) jump 1b;\n"                    \
  82                 "2:\n"                                          \
  83                 : "=&r" (__oldval)                              \
  84                 : "r" (__ptr), "r" (__old), "r" (__new)         \
  85                 : "memory", "p0"                                \
  86         );                                                      \
  87         __oldval;                                               \
  88 })
  89
  90 #endif /* _ASM_CMPXCHG_H */