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- /*
- * This file is part of the libopencm3 project.
- *
- * Copyright (C) 2012 Fergus Noble <fergusnoble@gmail.com>
- *
- * This library is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this library. If not, see <http://www.gnu.org/licenses/>.
- */
-
- #include <libopencm3/cm3/sync.h>
-
- /* DMB is supported on CM0 */
- void __dmb()
- {
- __asm__ volatile ("dmb");
- }
-
- /* Those are defined only on CM3 or CM4 */
- #if defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7EM__)
-
- uint32_t __ldrex(volatile uint32_t *addr)
- {
- uint32_t res;
- __asm__ volatile ("ldrex %0, [%1]" : "=r" (res) : "r" (addr));
- return res;
- }
-
- uint32_t __strex(uint32_t val, volatile uint32_t *addr)
- {
- uint32_t res;
- __asm__ volatile ("strex %0, %2, [%1]"
- : "=&r" (res) : "r" (addr), "r" (val));
- return res;
- }
-
- void mutex_lock(mutex_t *m)
- {
- while (!mutex_trylock(m));
- }
-
- /* returns 1 if the lock was acquired */
- uint32_t mutex_trylock(mutex_t *m)
- {
- uint32_t status = 1;
-
- /* If the mutex is unlocked. */
- if (__ldrex(m) == MUTEX_UNLOCKED) {
- /* Try to lock it. */
- status = __strex(MUTEX_LOCKED, m);
- }
-
- /* Execute the mysterious Data Memory Barrier instruction! */
- __dmb();
-
- /* Did we get the lock? If not then try again
- * by calling this function once more. */
- return status == 0;
- }
-
- void mutex_unlock(mutex_t *m)
- {
- /* Ensure accesses to protected resource are finished */
- __dmb();
-
- /* Free the lock. */
- *m = MUTEX_UNLOCKED;
- }
-
- #endif
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