arch/xtensa/include/asm/cmpxchg.h

   1 /*
   2  * Atomic xchg and cmpxchg operations.
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 2001 - 2005 Tensilica Inc.
   9  */
  10
  11 #ifndef _XTENSA_CMPXCHG_H
  12 #define _XTENSA_CMPXCHG_H
  13
  14 #ifndef __ASSEMBLY__
  15
  16 #include <linux/stringify.h>
  17
  18 /*
  19  * cmpxchg
  20  */
  21
  22 static inline unsigned long
  23 __cmpxchg_u32(volatile int *p, int old, int new)
  24 {
  25 #if XCHAL_HAVE_S32C1I
  26         __asm__ __volatile__(
  27                         "       wsr     %2, scompare1\n"
  28                         "       s32c1i  %0, %1, 0\n"
  29                         : "+a" (new)
  30                         : "a" (p), "a" (old)
  31                         : "memory"
  32                         );
  33
  34         return new;
  35 #else
  36         __asm__ __volatile__(
  37                         "       rsil    a15, "__stringify(TOPLEVEL)"\n"
  38                         "       l32i    %0, %1, 0\n"
  39                         "       bne     %0, %2, 1f\n"
  40                         "       s32i    %3, %1, 0\n"
  41                         "1:\n"
  42                         "       wsr     a15, ps\n"
  43                         "       rsync\n"
  44                         : "=&a" (old)
  45                         : "a" (p), "a" (old), "r" (new)
  46                         : "a15", "memory");
  47         return old;
  48 #endif
  49 }
  50 /* This function doesn't exist, so you'll get a linker error
  51  * if something tries to do an invalid cmpxchg(). */
  52
  53 extern void __cmpxchg_called_with_bad_pointer(void);
  54
  55 static __inline__ unsigned long
  56 __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
  57 {
  58         switch (size) {
  59         case 4:  return __cmpxchg_u32(ptr, old, new);
  60         default: __cmpxchg_called_with_bad_pointer();
  61                  return old;
  62         }
  63 }
  64
  65 #define cmpxchg(ptr,o,n)                                                      \
  66         ({ __typeof__(*(ptr)) _o_ = (o);                                      \
  67            __typeof__(*(ptr)) _n_ = (n);                                      \
  68            (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_,          \
  69                                         (unsigned long)_n_, sizeof (*(ptr))); \
  70         })
  71
  72 #include <asm-generic/cmpxchg-local.h>
  73
  74 static inline unsigned long __cmpxchg_local(volatile void *ptr,
  75                                       unsigned long old,
  76                                       unsigned long new, int size)
  77 {
  78         switch (size) {
  79         case 4:
  80                 return __cmpxchg_u32(ptr, old, new);
  81         default:
  82                 return __cmpxchg_local_generic(ptr, old, new, size);
  83         }
  84
  85         return old;
  86 }
  87
  88 /*
  89  * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
  90  * them available.
  91  */
  92 #define cmpxchg_local(ptr, o, n)                                               \
  93         ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
  94                         (unsigned long)(n), sizeof(*(ptr))))
  95 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
  96 #define cmpxchg64(ptr, o, n)    cmpxchg64_local((ptr), (o), (n))
  97
  98 /*
  99  * xchg_u32
 100  *
 101  * Note that a15 is used here because the register allocation
 102  * done by the compiler is not guaranteed and a window overflow
 103  * may not occur between the rsil and wsr instructions. By using
 104  * a15 in the rsil, the machine is guaranteed to be in a state
 105  * where no register reference will cause an overflow.
 106  */
 107
 108 static inline unsigned long xchg_u32(volatile int * m, unsigned long val)
 109 {
 110 #if XCHAL_HAVE_S32C1I
 111         unsigned long tmp, result;
 112         __asm__ __volatile__(
 113                         "1:     l32i    %1, %2, 0\n"
 114                         "       mov     %0, %3\n"
 115                         "       wsr     %1, scompare1\n"
 116                         "       s32c1i  %0, %2, 0\n"
 117                         "       bne     %0, %1, 1b\n"
 118                         : "=&a" (result), "=&a" (tmp)
 119                         : "a" (m), "a" (val)
 120                         : "memory"
 121                         );
 122         return result;
 123 #else
 124         unsigned long tmp;
 125         __asm__ __volatile__(
 126                         "       rsil    a15, "__stringify(TOPLEVEL)"\n"
 127                         "       l32i    %0, %1, 0\n"
 128                         "       s32i    %2, %1, 0\n"
 129                         "       wsr     a15, ps\n"
 130                         "       rsync\n"
 131                         : "=&a" (tmp)
 132                         : "a" (m), "a" (val)
 133                         : "a15", "memory");
 134         return tmp;
 135 #endif
 136 }
 137
 138 #define xchg(ptr,x) \
 139         ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
 140
 141 /*
 142  * This only works if the compiler isn't horribly bad at optimizing.
 143  * gcc-2.5.8 reportedly can't handle this, but I define that one to
 144  * be dead anyway.
 145  */
 146
 147 extern void __xchg_called_with_bad_pointer(void);
 148
 149 static __inline__ unsigned long
 150 __xchg(unsigned long x, volatile void * ptr, int size)
 151 {
 152         switch (size) {
 153                 case 4:
 154                         return xchg_u32(ptr, x);
 155         }
 156         __xchg_called_with_bad_pointer();
 157         return x;
 158 }
 159
 160 #endif /* __ASSEMBLY__ */
 161
 162 #endif /* _XTENSA_CMPXCHG_H */