80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
|
/*
|
||
|
|
* 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
|