| 1 | /* |
| 2 | * arch/ubicom32/include/asm/spinlock.h |
| 3 | * Spinlock related definitions for Ubicom32 architecture. |
| 4 | * |
| 5 | * (C) Copyright 2009, Ubicom, Inc. |
| 6 | * |
| 7 | * This file is part of the Ubicom32 Linux Kernel Port. |
| 8 | * |
| 9 | * The Ubicom32 Linux Kernel Port is free software: you can redistribute |
| 10 | * it and/or modify it under the terms of the GNU General Public License |
| 11 | * as published by the Free Software Foundation, either version 2 of the |
| 12 | * License, or (at your option) any later version. |
| 13 | * |
| 14 | * The Ubicom32 Linux Kernel Port is distributed in the hope that it |
| 15 | * will be useful, but WITHOUT ANY WARRANTY; without even the implied |
| 16 | * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See |
| 17 | * the GNU General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU General Public License |
| 20 | * along with the Ubicom32 Linux Kernel Port. If not, |
| 21 | * see <http://www.gnu.org/licenses/>. |
| 22 | * |
| 23 | * Ubicom32 implementation derived from (with many thanks): |
| 24 | * arch/m68knommu |
| 25 | * arch/blackfin |
| 26 | * arch/parisc |
| 27 | */ |
| 28 | #ifndef _ASM_UBICOM32_SPINLOCK_H |
| 29 | #define _ASM_UBICOM32_SPINLOCK_H |
| 30 | |
| 31 | #include <asm/system.h> |
| 32 | #include <asm/processor.h> |
| 33 | #include <asm/spinlock_types.h> |
| 34 | |
| 35 | /* |
| 36 | * __raw_spin_lock() |
| 37 | * Lock the lock. |
| 38 | */ |
| 39 | static inline void __raw_spin_lock(raw_spinlock_t *x) |
| 40 | { |
| 41 | asm volatile ( |
| 42 | "1: bset %0, %0, #0 \n\t" |
| 43 | " jmpne.f 1b \n\t" |
| 44 | : "+U4" (x->lock) |
| 45 | : |
| 46 | : "memory", "cc" |
| 47 | ); |
| 48 | } |
| 49 | |
| 50 | /* |
| 51 | * __raw_spin_unlock() |
| 52 | * Unlock the lock. |
| 53 | */ |
| 54 | static inline void __raw_spin_unlock(raw_spinlock_t *x) |
| 55 | { |
| 56 | asm volatile ( |
| 57 | " bclr %0, %0, #0 \n\t" |
| 58 | : "+U4" (x->lock) |
| 59 | : |
| 60 | : "memory", "cc" |
| 61 | ); |
| 62 | } |
| 63 | |
| 64 | /* |
| 65 | * __raw_spin_is_locked() |
| 66 | * Test if the lock is locked. |
| 67 | */ |
| 68 | static inline int __raw_spin_is_locked(raw_spinlock_t *x) |
| 69 | { |
| 70 | return x->lock; |
| 71 | } |
| 72 | |
| 73 | /* |
| 74 | * __raw_spin_unlock_wait() |
| 75 | * Wait for the lock to be unlocked. |
| 76 | * |
| 77 | * Note: the caller has not guarantee that the lock will not |
| 78 | * be acquired before they get to it. |
| 79 | */ |
| 80 | static inline void __raw_spin_unlock_wait(raw_spinlock_t *x) |
| 81 | { |
| 82 | do { |
| 83 | cpu_relax(); |
| 84 | } while (__raw_spin_is_locked(x)); |
| 85 | } |
| 86 | |
| 87 | /* |
| 88 | * __raw_spin_trylock() |
| 89 | * Try the lock, return 0 on failure, 1 on success. |
| 90 | */ |
| 91 | static inline int __raw_spin_trylock(raw_spinlock_t *x) |
| 92 | { |
| 93 | int ret = 0; |
| 94 | |
| 95 | asm volatile ( |
| 96 | " bset %1, %1, #0 \n\t" |
| 97 | " jmpne.f 1f \n\t" |
| 98 | " move.4 %0, #1 \n\t" |
| 99 | "1: \n\t" |
| 100 | : "+r" (ret), "+U4" (x->lock) |
| 101 | : |
| 102 | : "memory", "cc" |
| 103 | ); |
| 104 | |
| 105 | return ret; |
| 106 | } |
| 107 | |
| 108 | /* |
| 109 | * __raw_spin_lock_flags() |
| 110 | * Spin waiting for the lock (enabling IRQ(s)) |
| 111 | */ |
| 112 | static inline void __raw_spin_lock_flags(raw_spinlock_t *x, unsigned long flags) |
| 113 | { |
| 114 | mb(); |
| 115 | while (!__raw_spin_trylock(x)) { |
| 116 | /* |
| 117 | * If the flags from the IRQ are set, interrupts are disabled and we |
| 118 | * need to re-enable them. |
| 119 | */ |
| 120 | if (!flags) { |
| 121 | cpu_relax(); |
| 122 | } else { |
| 123 | raw_local_irq_enable(); |
| 124 | cpu_relax(); |
| 125 | raw_local_irq_disable(); |
| 126 | } |
| 127 | } |
| 128 | mb(); |
| 129 | } |
| 130 | |
| 131 | /* |
| 132 | * Read-write spinlocks, allowing multiple readers but only one writer. |
| 133 | * Linux rwlocks are unfair to writers; they can be starved for an indefinite |
| 134 | * time by readers. With care, they can also be taken in interrupt context. |
| 135 | * |
| 136 | * In Ubicom32 architecture implementation, we have a spinlock and a counter. |
| 137 | * Readers use the lock to serialise their access to the counter (which |
| 138 | * records how many readers currently hold the lock). |
| 139 | * Writers hold the spinlock, preventing any readers or other writers from |
| 140 | * grabbing the rwlock. |
| 141 | */ |
| 142 | |
| 143 | /* |
| 144 | * __raw_read_lock() |
| 145 | * Increment the counter in the rwlock. |
| 146 | * |
| 147 | * Note that we have to ensure interrupts are disabled in case we're |
| 148 | * interrupted by some other code that wants to grab the same read lock |
| 149 | */ |
| 150 | static inline void __raw_read_lock(raw_rwlock_t *rw) |
| 151 | { |
| 152 | unsigned long flags; |
| 153 | raw_local_irq_save(flags); |
| 154 | __raw_spin_lock_flags(&rw->lock, flags); |
| 155 | rw->counter++; |
| 156 | __raw_spin_unlock(&rw->lock); |
| 157 | raw_local_irq_restore(flags); |
| 158 | } |
| 159 | |
| 160 | /* |
| 161 | * __raw_read_unlock() |
| 162 | * Decrement the counter. |
| 163 | * |
| 164 | * Note that we have to ensure interrupts are disabled in case we're |
| 165 | * interrupted by some other code that wants to grab the same read lock |
| 166 | */ |
| 167 | static inline void __raw_read_unlock(raw_rwlock_t *rw) |
| 168 | { |
| 169 | unsigned long flags; |
| 170 | raw_local_irq_save(flags); |
| 171 | __raw_spin_lock_flags(&rw->lock, flags); |
| 172 | rw->counter--; |
| 173 | __raw_spin_unlock(&rw->lock); |
| 174 | raw_local_irq_restore(flags); |
| 175 | } |
| 176 | |
| 177 | /* |
| 178 | * __raw_read_trylock() |
| 179 | * Increment the counter if we can. |
| 180 | * |
| 181 | * Note that we have to ensure interrupts are disabled in case we're |
| 182 | * interrupted by some other code that wants to grab the same read lock |
| 183 | */ |
| 184 | static inline int __raw_read_trylock(raw_rwlock_t *rw) |
| 185 | { |
| 186 | unsigned long flags; |
| 187 | retry: |
| 188 | raw_local_irq_save(flags); |
| 189 | if (__raw_spin_trylock(&rw->lock)) { |
| 190 | rw->counter++; |
| 191 | __raw_spin_unlock(&rw->lock); |
| 192 | raw_local_irq_restore(flags); |
| 193 | return 1; |
| 194 | } |
| 195 | |
| 196 | raw_local_irq_restore(flags); |
| 197 | |
| 198 | /* |
| 199 | * If write-locked, we fail to acquire the lock |
| 200 | */ |
| 201 | if (rw->counter < 0) { |
| 202 | return 0; |
| 203 | } |
| 204 | |
| 205 | /* |
| 206 | * Wait until we have a realistic chance at the lock |
| 207 | */ |
| 208 | while (__raw_spin_is_locked(&rw->lock) && rw->counter >= 0) { |
| 209 | cpu_relax(); |
| 210 | } |
| 211 | |
| 212 | goto retry; |
| 213 | } |
| 214 | |
| 215 | /* |
| 216 | * __raw_write_lock() |
| 217 | * |
| 218 | * Note that we have to ensure interrupts are disabled in case we're |
| 219 | * interrupted by some other code that wants to read_trylock() this lock |
| 220 | */ |
| 221 | static inline void __raw_write_lock(raw_rwlock_t *rw) |
| 222 | { |
| 223 | unsigned long flags; |
| 224 | retry: |
| 225 | raw_local_irq_save(flags); |
| 226 | __raw_spin_lock_flags(&rw->lock, flags); |
| 227 | |
| 228 | if (rw->counter != 0) { |
| 229 | __raw_spin_unlock(&rw->lock); |
| 230 | raw_local_irq_restore(flags); |
| 231 | |
| 232 | while (rw->counter != 0) |
| 233 | cpu_relax(); |
| 234 | |
| 235 | goto retry; |
| 236 | } |
| 237 | |
| 238 | rw->counter = -1; /* mark as write-locked */ |
| 239 | mb(); |
| 240 | raw_local_irq_restore(flags); |
| 241 | } |
| 242 | |
| 243 | static inline void __raw_write_unlock(raw_rwlock_t *rw) |
| 244 | { |
| 245 | rw->counter = 0; |
| 246 | __raw_spin_unlock(&rw->lock); |
| 247 | } |
| 248 | |
| 249 | /* Note that we have to ensure interrupts are disabled in case we're |
| 250 | * interrupted by some other code that wants to read_trylock() this lock */ |
| 251 | static inline int __raw_write_trylock(raw_rwlock_t *rw) |
| 252 | { |
| 253 | unsigned long flags; |
| 254 | int result = 0; |
| 255 | |
| 256 | raw_local_irq_save(flags); |
| 257 | if (__raw_spin_trylock(&rw->lock)) { |
| 258 | if (rw->counter == 0) { |
| 259 | rw->counter = -1; |
| 260 | result = 1; |
| 261 | } else { |
| 262 | /* Read-locked. Oh well. */ |
| 263 | __raw_spin_unlock(&rw->lock); |
| 264 | } |
| 265 | } |
| 266 | raw_local_irq_restore(flags); |
| 267 | |
| 268 | return result; |
| 269 | } |
| 270 | |
| 271 | /* |
| 272 | * read_can_lock - would read_trylock() succeed? |
| 273 | * @lock: the rwlock in question. |
| 274 | */ |
| 275 | static inline int __raw_read_can_lock(raw_rwlock_t *rw) |
| 276 | { |
| 277 | return rw->counter >= 0; |
| 278 | } |
| 279 | |
| 280 | /* |
| 281 | * write_can_lock - would write_trylock() succeed? |
| 282 | * @lock: the rwlock in question. |
| 283 | */ |
| 284 | static inline int __raw_write_can_lock(raw_rwlock_t *rw) |
| 285 | { |
| 286 | return !rw->counter; |
| 287 | } |
| 288 | |
| 289 | #define __raw_read_lock_flags(lock, flags) __raw_read_lock(lock) |
| 290 | #define __raw_write_lock_flags(lock, flags) __raw_write_lock(lock) |
| 291 | |
| 292 | #define _raw_spin_relax(lock) cpu_relax() |
| 293 | #define _raw_read_relax(lock) cpu_relax() |
| 294 | #define _raw_write_relax(lock) cpu_relax() |
| 295 | |
| 296 | #endif /* _ASM_UBICOM32_SPINLOCK_H */ |
| 297 | |
