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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();
}
