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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)
{
uint32_t status = 0;
do {
/* Wait until the mutex is unlocked. */
while (__ldrex(m) != MUTEX_UNLOCKED);
/* Try to acquire it. */
status = __strex(MUTEX_LOCKED, m);
/* Did we get it? If not then try again. */
} while (status != 0);
/* Execute the mysterious Data Memory Barrier instruction! */
__dmb();
}
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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