mxc_lock.c

/* ****************************************************************************
 * Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
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 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * Except as contained in this notice, the name of Maxim Integrated
 * Products, Inc. shall not be used except as stated in the Maxim Integrated
 * Products, Inc. Branding Policy.
 *
 * The mere transfer of this software does not imply any licenses
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 * $Date: 2018-08-28 22:06:43 +0000 (Tue, 28 Aug 2018) $
 * $Revision: 37425 $
 *
 *************************************************************************** */

/* **** Includes **** */
#include "mxc_config.h"
#include "mxc_lock.h"


/* ************************************************************************** */
int mxc_get_lock(uint32_t *lock, uint32_t value)
{
    do {
    
        // Return if the lock is taken by a different thread
        if (__LDREXW((volatile unsigned long *)lock) != 0) {
            return E_BUSY;
        }
        
        // Attempt to take the lock
    } while (__STREXW(value, (volatile unsigned long *)lock) != 0);
    
    // Do not start any other memory access until memory barrier is complete
    __DMB();
    
    return E_NO_ERROR;
}

/* ************************************************************************** */
void mxc_free_lock(uint32_t *lock)
{
    // Ensure memory operations complete before releasing lock
    __DMB();
    *lock = 0;
}