mirror of https://github.com/ARMmbed/mbed-os.git
115 lines
3.8 KiB
C
115 lines
3.8 KiB
C
/**
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* @file
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* @brief Exclusive access lock utility functions.
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*/
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/* ****************************************************************************
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* Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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* Except as contained in this notice, the name of Maxim Integrated
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* Products, Inc. shall not be used except as stated in the Maxim Integrated
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* Products, Inc. Branding Policy.
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*
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* The mere transfer of this software does not imply any licenses
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* of trade secrets, proprietary technology, copyrights, patents,
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* trademarks, maskwork rights, or any other form of intellectual
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* property whatsoever. Maxim Integrated Products, Inc. retains all
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* ownership rights.
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*
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* $Date: 2016-10-10 19:16:20 -0500 (Mon, 10 Oct 2016) $
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* $Revision: 24663 $
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*
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*************************************************************************** */
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/* Define to prevent redundant inclusion */
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#ifndef _MXC_LOCK_H_
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#define _MXC_LOCK_H_
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/***** Includes *****/
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#include "mxc_config.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @ingroup sysconfig
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* @defgroup mxc_lock_utilities Lock functions for Exclusive Access
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* @brief Lock functions to obtain and release a variable for exclusive
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* access. These functions are marked interrupt safe if they are
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* interrupt safe.
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* @{
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*/
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/* **** Definitions **** */
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/* **** Globals **** */
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/* **** Function Prototypes **** */
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/**
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* @brief Attempts to acquire the lock.
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* @details This in an interrupt safe function that can be used as a mutex.
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* The lock variable must remain in scope until the lock is
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* released. Will not block if another thread has already acquired
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* the lock.
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* @param lock Pointer to variable that is used for the lock.
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* @param value Value to be place in the lock. Can not be 0.
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*
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* @return #E_NO_ERROR if everything successful, #E_BUSY if lock is taken.
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*/
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__STATIC_INLINE int mxc_get_lock(uint32_t *lock, uint32_t value)
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{
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do {
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// Return if the lock is taken by a different thread
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if(__LDREXW((volatile uint32_t *)lock) != 0) {
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return E_BUSY;
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}
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// Attempt to take the lock
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} while(__STREXW(value, (volatile uint32_t *)lock) != 0);
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// Do not start any other memory access until memory barrier is complete
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__DMB();
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return E_NO_ERROR;
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}
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/**
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* @brief Free the given lock.
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* @param[in,out] lock Pointer to the variable used for the lock. When the lock
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* is free, the value pointed to by @p lock is set to zero.
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*/
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__STATIC_INLINE void mxc_free_lock(uint32_t *lock)
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{
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// Ensure memory operations complete before releasing lock
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__DMB();
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*lock = 0;
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}
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/**@} end of group mxc_lock_utilities */
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#ifdef __cplusplus
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}
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#endif
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#endif /* _MXC_LOCK_H_ */
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