arch/xtensa/include/asm/spinlock.h

   1 /*
   2  * include/asm-xtensa/spinlock.h
   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_SPINLOCK_H
  12 #define _XTENSA_SPINLOCK_H
  13
  14 #include <asm/barrier.h>
  15 #include <asm/processor.h>
  16
  17 /*
  18  * spinlock
  19  *
  20  * There is at most one owner of a spinlock.  There are not different
  21  * types of spinlock owners like there are for rwlocks (see below).
  22  *
  23  * When trying to obtain a spinlock, the function "spins" forever, or busy-
  24  * waits, until the lock is obtained.  When spinning, presumably some other
  25  * owner will soon give up the spinlock making it available to others.  Use
  26  * the trylock functions to avoid spinning forever.
  27  *
  28  * possible values:
  29  *
  30  *    0         nobody owns the spinlock
  31  *    1         somebody owns the spinlock
  32  */
  33
  34 #define arch_spin_is_locked(x) ((x)->slock != 0)
  35
  36 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
  37 {
  38         smp_cond_load_acquire(&lock->slock, !VAL);
  39 }
  40
  41 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
  42
  43 static inline void arch_spin_lock(arch_spinlock_t *lock)
  44 {
  45         unsigned long tmp;
  46
  47         __asm__ __volatile__(
  48                         "       movi    %0, 0\n"
  49                         "       wsr     %0, scompare1\n"
  50                         "1:     movi    %0, 1\n"
  51                         "       s32c1i  %0, %1, 0\n"
  52                         "       bnez    %0, 1b\n"
  53                         : "=&a" (tmp)
  54                         : "a" (&lock->slock)
  55                         : "memory");
  56 }
  57
  58 /* Returns 1 if the lock is obtained, 0 otherwise. */
  59
  60 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  61 {
  62         unsigned long tmp;
  63
  64         __asm__ __volatile__(
  65                         "       movi    %0, 0\n"
  66                         "       wsr     %0, scompare1\n"
  67                         "       movi    %0, 1\n"
  68                         "       s32c1i  %0, %1, 0\n"
  69                         : "=&a" (tmp)
  70                         : "a" (&lock->slock)
  71                         : "memory");
  72
  73         return tmp == 0 ? 1 : 0;
  74 }
  75
  76 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  77 {
  78         unsigned long tmp;
  79
  80         __asm__ __volatile__(
  81                         "       movi    %0, 0\n"
  82                         "       s32ri   %0, %1, 0\n"
  83                         : "=&a" (tmp)
  84                         : "a" (&lock->slock)
  85                         : "memory");
  86 }
  87
  88 /*
  89  * rwlock
  90  *
  91  * Read-write locks are really a more flexible spinlock.  They allow
  92  * multiple readers but only one writer.  Write ownership is exclusive
  93  * (i.e., all other readers and writers are blocked from ownership while
  94  * there is a write owner).  These rwlocks are unfair to writers.  Writers
  95  * can be starved for an indefinite time by readers.
  96  *
  97  * possible values:
  98  *
  99  *   0          nobody owns the rwlock
 100  *  >0          one or more readers own the rwlock
 101  *                (the positive value is the actual number of readers)
 102  *  0x80000000  one writer owns the rwlock, no other writers, no readers
 103  */
 104
 105 #define arch_write_can_lock(x)  ((x)->lock == 0)
 106
 107 static inline void arch_write_lock(arch_rwlock_t *rw)
 108 {
 109         unsigned long tmp;
 110
 111         __asm__ __volatile__(
 112                         "       movi    %0, 0\n"
 113                         "       wsr     %0, scompare1\n"
 114                         "1:     movi    %0, 1\n"
 115                         "       slli    %0, %0, 31\n"
 116                         "       s32c1i  %0, %1, 0\n"
 117                         "       bnez    %0, 1b\n"
 118                         : "=&a" (tmp)
 119                         : "a" (&rw->lock)
 120                         : "memory");
 121 }
 122
 123 /* Returns 1 if the lock is obtained, 0 otherwise. */
 124
 125 static inline int arch_write_trylock(arch_rwlock_t *rw)
 126 {
 127         unsigned long tmp;
 128
 129         __asm__ __volatile__(
 130                         "       movi    %0, 0\n"
 131                         "       wsr     %0, scompare1\n"
 132                         "       movi    %0, 1\n"
 133                         "       slli    %0, %0, 31\n"
 134                         "       s32c1i  %0, %1, 0\n"
 135                         : "=&a" (tmp)
 136                         : "a" (&rw->lock)
 137                         : "memory");
 138
 139         return tmp == 0 ? 1 : 0;
 140 }
 141
 142 static inline void arch_write_unlock(arch_rwlock_t *rw)
 143 {
 144         unsigned long tmp;
 145
 146         __asm__ __volatile__(
 147                         "       movi    %0, 0\n"
 148                         "       s32ri   %0, %1, 0\n"
 149                         : "=&a" (tmp)
 150                         : "a" (&rw->lock)
 151                         : "memory");
 152 }
 153
 154 static inline void arch_read_lock(arch_rwlock_t *rw)
 155 {
 156         unsigned long tmp;
 157         unsigned long result;
 158
 159         __asm__ __volatile__(
 160                         "1:     l32i    %1, %2, 0\n"
 161                         "       bltz    %1, 1b\n"
 162                         "       wsr     %1, scompare1\n"
 163                         "       addi    %0, %1, 1\n"
 164                         "       s32c1i  %0, %2, 0\n"
 165                         "       bne     %0, %1, 1b\n"
 166                         : "=&a" (result), "=&a" (tmp)
 167                         : "a" (&rw->lock)
 168                         : "memory");
 169 }
 170
 171 /* Returns 1 if the lock is obtained, 0 otherwise. */
 172
 173 static inline int arch_read_trylock(arch_rwlock_t *rw)
 174 {
 175         unsigned long result;
 176         unsigned long tmp;
 177
 178         __asm__ __volatile__(
 179                         "       l32i    %1, %2, 0\n"
 180                         "       addi    %0, %1, 1\n"
 181                         "       bltz    %0, 1f\n"
 182                         "       wsr     %1, scompare1\n"
 183                         "       s32c1i  %0, %2, 0\n"
 184                         "       sub     %0, %0, %1\n"
 185                         "1:\n"
 186                         : "=&a" (result), "=&a" (tmp)
 187                         : "a" (&rw->lock)
 188                         : "memory");
 189
 190         return result == 0;
 191 }
 192
 193 static inline void arch_read_unlock(arch_rwlock_t *rw)
 194 {
 195         unsigned long tmp1, tmp2;
 196
 197         __asm__ __volatile__(
 198                         "1:     l32i    %1, %2, 0\n"
 199                         "       addi    %0, %1, -1\n"
 200                         "       wsr     %1, scompare1\n"
 201                         "       s32c1i  %0, %2, 0\n"
 202                         "       bne     %0, %1, 1b\n"
 203                         : "=&a" (tmp1), "=&a" (tmp2)
 204                         : "a" (&rw->lock)
 205                         : "memory");
 206 }
 207
 208 #define arch_read_lock_flags(lock, flags)       arch_read_lock(lock)
 209 #define arch_write_lock_flags(lock, flags)      arch_write_lock(lock)
 210
 211 #endif  /* _XTENSA_SPINLOCK_H */