FreeRTOS/Demo/CORTEX_M7_SAMV71_Xplained_AtmelStudio/libchip_samv7/source/mpu.c

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 *         SAM Software Package License 
 * ----------------------------------------------------------------------------
 * Copyright (c) 2014, Atmel Corporation
 *
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 * modification, are permitted provided that the following conditions are met:
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/** \file */

/** 
 * \addtogroup mmu MMU Initialization
 *
 * \section Usage
 *
 * Translation Look-aside Buffers (TLBs) are an implementation technique that 
 * caches translations or translation table entries. TLBs avoid the requirement 
 * for every memory access to perform a translation table lookup. 
 * The ARM architecture does not specify the exact form of the TLB structures 
 * for any design. In a similar way to the requirements for caches, the 
 * architecture only defines certain principles for TLBs:
 * 
 * The MMU supports memory accesses based on memory sections or pages:
 * Super-sections Consist of 16MB blocks of memory. Support for Super sections 
 * is optional.
 * -# Sections Consist of 1MB blocks of memory.
 * -# Large pages Consist of 64KB blocks of memory.
 * -# Small pages Consist of 4KB blocks of memory.
 *
 * Access to a memory region is controlled by the access permission bits and 
 * the domain field in the TLB entry.
 * Memory region attributes
 * Each TLB entry has an associated set of memory region attributes. These 
 * control accesses to the caches,
 * how the write buffer is used, and if the memory region is Shareable and 
 * therefore must be kept coherent.
 *
 * Related files:\n
 * \ref mmu.c\n
 * \ref mmu.h \n
 */

/*-------------------------------------------------------------------------- */
/*         Headers                                                           */
/*-------------------------------------------------------------------------- */
#include <chip.h>

/*----------------------------------------------------------------------------
 *        Exported functions

 *----------------------------------------------------------------------------*/
/**
 * \brief Enables the MPU module.
 *
 * \param dwMPUEnable  Enable/Disable the memory region.
 */
void MPU_Enable( uint32_t dwMPUEnable )
{
	MPU->CTRL = dwMPUEnable ;
}

/**
 * \brief Set active memory region.
 *
 * \param dwRegionNum  The memory region to be active.
 */
void MPU_SetRegionNum( uint32_t dwRegionNum )
{
	MPU->RNR = dwRegionNum;
}

/**
 * \brief Disable the current active region.
 */
extern void MPU_DisableRegion( void )
{
	MPU->RASR &= 0xfffffffe;
}

/**
 * \brief Setup a memory region.
 *
 * \param dwRegionBaseAddr  Memory region base address.
 * \param dwRegionAttr  Memory region attributes.  
 */
void MPU_SetRegion( uint32_t dwRegionBaseAddr, uint32_t dwRegionAttr )
{
	MPU->RBAR = dwRegionBaseAddr;
	MPU->RASR = dwRegionAttr;
}


/**
 * \brief Calculate region size for the RASR.
 */
uint32_t MPU_CalMPURegionSize( uint32_t dwActualSizeInBytes )
{
	uint32_t dwRegionSize = 32;
	uint32_t dwReturnValue = 4;

	while( dwReturnValue < 31 ) {
		if( dwActualSizeInBytes <= dwRegionSize ) {
			break;
		} else {
			dwReturnValue++;
		}
		dwRegionSize <<= 1;
	}

	return ( dwReturnValue << 1 );
}


/**
 *  \brief Update MPU regions.
 *
 *  \return Unused (ANSI-C compatibility).
 */
void MPU_UpdateRegions( uint32_t dwRegionNum, uint32_t dwRegionBaseAddr,
		uint32_t dwRegionAttr)
{
	
	/* Disable interrupt */
	__disable_irq();

	/* Clean up data and instruction buffer */
	__DSB();
	__ISB();

	/* Set active region */
	MPU_SetRegionNum(dwRegionNum);

	/* Disable region */
	MPU_DisableRegion();

	/* Update region attribute */
	MPU_SetRegion( dwRegionBaseAddr, dwRegionAttr);

	/* Clean up data and instruction buffer to make the new region taking 
	   effect at once */
	__DSB();
	__ISB();

	/* Enable the interrupt */
	__enable_irq();
}