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 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
  37
  38 static inline void arch_spin_lock(arch_spinlock_t *lock)
  39 {
  40         unsigned long tmp;
  41
  42         __asm__ __volatile__(
  43                         "       movi    %0, 0\n"
  44                         "       wsr     %0, scompare1\n"
  45                         "1:     movi    %0, 1\n"
  46                         "       s32c1i  %0, %1, 0\n"
  47                         "       bnez    %0, 1b\n"
  48                         : "=&a" (tmp)
  49                         : "a" (&lock->slock)
  50                         : "memory");
  51 }
  52
  53 /* Returns 1 if the lock is obtained, 0 otherwise. */
  54
  55 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  56 {
  57         unsigned long tmp;
  58
  59         __asm__ __volatile__(
  60                         "       movi    %0, 0\n"
  61                         "       wsr     %0, scompare1\n"
  62                         "       movi    %0, 1\n"
  63                         "       s32c1i  %0, %1, 0\n"
  64                         : "=&a" (tmp)
  65                         : "a" (&lock->slock)
  66                         : "memory");
  67
  68         return tmp == 0 ? 1 : 0;
  69 }
  70
  71 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  72 {
  73         unsigned long tmp;
  74
  75         __asm__ __volatile__(
  76                         "       movi    %0, 0\n"
  77                         "       s32ri   %0, %1, 0\n"
  78                         : "=&a" (tmp)
  79                         : "a" (&lock->slock)
  80                         : "memory");
  81 }
  82
  83 /*
  84  * rwlock
  85  *
  86  * Read-write locks are really a more flexible spinlock.  They allow
  87  * multiple readers but only one writer.  Write ownership is exclusive
  88  * (i.e., all other readers and writers are blocked from ownership while
  89  * there is a write owner).  These rwlocks are unfair to writers.  Writers
  90  * can be starved for an indefinite time by readers.
  91  *
  92  * possible values:
  93  *
  94  *   0          nobody owns the rwlock
  95  *  >0          one or more readers own the rwlock
  96  *                (the positive value is the actual number of readers)
  97  *  0x80000000  one writer owns the rwlock, no other writers, no readers
  98  */
  99
 100 #define arch_write_can_lock(x)  ((x)->lock == 0)
 101
 102 static inline void arch_write_lock(arch_rwlock_t *rw)
 103 {
 104         unsigned long tmp;
 105
 106         __asm__ __volatile__(
 107                         "       movi    %0, 0\n"
 108                         "       wsr     %0, scompare1\n"
 109                         "1:     movi    %0, 1\n"
 110                         "       slli    %0, %0, 31\n"
 111                         "       s32c1i  %0, %1, 0\n"
 112                         "       bnez    %0, 1b\n"
 113                         : "=&a" (tmp)
 114                         : "a" (&rw->lock)
 115                         : "memory");
 116 }
 117
 118 /* Returns 1 if the lock is obtained, 0 otherwise. */
 119
 120 static inline int arch_write_trylock(arch_rwlock_t *rw)
 121 {
 122         unsigned long tmp;
 123
 124         __asm__ __volatile__(
 125                         "       movi    %0, 0\n"
 126                         "       wsr     %0, scompare1\n"
 127                         "       movi    %0, 1\n"
 128                         "       slli    %0, %0, 31\n"
 129                         "       s32c1i  %0, %1, 0\n"
 130                         : "=&a" (tmp)
 131                         : "a" (&rw->lock)
 132                         : "memory");
 133
 134         return tmp == 0 ? 1 : 0;
 135 }
 136
 137 static inline void arch_write_unlock(arch_rwlock_t *rw)
 138 {
 139         unsigned long tmp;
 140
 141         __asm__ __volatile__(
 142                         "       movi    %0, 0\n"
 143                         "       s32ri   %0, %1, 0\n"
 144                         : "=&a" (tmp)
 145                         : "a" (&rw->lock)
 146                         : "memory");
 147 }
 148
 149 static inline void arch_read_lock(arch_rwlock_t *rw)
 150 {
 151         unsigned long tmp;
 152         unsigned long result;
 153
 154         __asm__ __volatile__(
 155                         "1:     l32i    %1, %2, 0\n"
 156                         "       bltz    %1, 1b\n"
 157                         "       wsr     %1, scompare1\n"
 158                         "       addi    %0, %1, 1\n"
 159                         "       s32c1i  %0, %2, 0\n"
 160                         "       bne     %0, %1, 1b\n"
 161                         : "=&a" (result), "=&a" (tmp)
 162                         : "a" (&rw->lock)
 163                         : "memory");
 164 }
 165
 166 /* Returns 1 if the lock is obtained, 0 otherwise. */
 167
 168 static inline int arch_read_trylock(arch_rwlock_t *rw)
 169 {
 170         unsigned long result;
 171         unsigned long tmp;
 172
 173         __asm__ __volatile__(
 174                         "       l32i    %1, %2, 0\n"
 175                         "       addi    %0, %1, 1\n"
 176                         "       bltz    %0, 1f\n"
 177                         "       wsr     %1, scompare1\n"
 178                         "       s32c1i  %0, %2, 0\n"
 179                         "       sub     %0, %0, %1\n"
 180                         "1:\n"
 181                         : "=&a" (result), "=&a" (tmp)
 182                         : "a" (&rw->lock)
 183                         : "memory");
 184
 185         return result == 0;
 186 }
 187
 188 static inline void arch_read_unlock(arch_rwlock_t *rw)
 189 {
 190         unsigned long tmp1, tmp2;
 191
 192         __asm__ __volatile__(
 193                         "1:     l32i    %1, %2, 0\n"
 194                         "       addi    %0, %1, -1\n"
 195                         "       wsr     %1, scompare1\n"
 196                         "       s32c1i  %0, %2, 0\n"
 197                         "       bne     %0, %1, 1b\n"
 198                         : "=&a" (tmp1), "=&a" (tmp2)
 199                         : "a" (&rw->lock)
 200                         : "memory");
 201 }
 202
 203 #define arch_read_lock_flags(lock, flags)       arch_read_lock(lock)
 204 #define arch_write_lock_flags(lock, flags)      arch_write_lock(lock)
 205
 206 #endif  /* _XTENSA_SPINLOCK_H */