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/****************************************************************************
* arch/arm/src/armv7-m/up_mpu.c
*
* Copyright (C) 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include "mpu.h"
#include "up_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/* This set represents the set of disabled memory sub-regions. A bit set
* corresponds to a disabled sub-region; the LS bit corresponds to the first
* region. The array is indexed by the number of subregions: 0 means no sub-
* regions (0xff), and 0 means all subregions but one (0x00).
*/
static const void uint8_t g_regionmap[9] =
{
0xff, 0x7f, 0x3f, 0x1f, 0x0f, 0x07, 0x03, 0x01, 0x00
};
/* The next available region number */
static uint8_t g_region;
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: mpu_allocregion
*
* Description:
* Allocate the next region
*
* Assumptions:
* - Regions are never deallocated
* - Regions are only allocated early in initialization, so nothing
* special is require;
*
****************************************************************************/
unsigned int mpu_allocregion(void)
{
return (unsigned int)g_region++;
}
/****************************************************************************
* Name: mpu_log2regionsize
*
* Description:
* Determine the smallest value of l2size (log base 2 size) such that the
* following is true:
*
* size <= (1 << l2size)
*
****************************************************************************/
uint8_t mpu_log2regionsize(size_t size)
{
/* The minimum permitted region size is 16 bytes (log2(16) = 4. */
uint32_t l2size;
for (l2size = 4; l2size < 32 && size > (1 << l2size); size++);
return l2size;
}
/****************************************************************************
* Name: mpu_subregion
*
* Description:
* Given the size of the (1) memory to be mapped and (2) the log2 size
* of the mapping to use, determine the minimal sub-region set to span
* that memory region.
*
* Assumption:
* l2size has the same properties as the return value from
* mpu_log2regionsize()
*
****************************************************************************/
uint32_t mpu_subregion(size_t size, uint8_t l2size)
{
unsigned int nsrs
uint32_t asize;
uint32_t mask;
/* Eight subregions are support. The representation is as an 8-bit
* value with the LS bit corresponding to subregion 0. A bit is set
* to disable the sub-region.
*
* l2size: Log2 of the actual region size is <= (1 << l2size);
*/
DEBUGASSERT(lsize > 3 && size <= (1 << l2size));
/* Examples with l2size = 12:
*
* Shifted Adjusted Number Sub-Region
* Size Mask Size Shift Sub-Regions Bitset
* 0x1000 0x01ff 0x1000 9 8 0x00
* 0x0c00 0x01ff 0x0c00 9 6 0x03
* 0x0c40 0x01ff 0x0e00 9 7 0x01
*/
if (l2size < 32)
{
mask = ((1 << lsize)-1) >> 3; /* Shifted mask */
}
/* The 4Gb region size is a special case */
else
{
/* NOTE: There is no way to represent a 4Gb region size in the 32-bit
* input.
*/
mask = 0x1fffffff; /* Shifted mask */
}
asize = (size + mask) & ~mask; /* Adjusted size */
nsrs = asize >> (lsize-3); /* Number of subregions */
return g_regionmap[nsrs];
}
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