diff options
Diffstat (limited to 'nuttx/arch/arm/src/armv7-m/up_mpu.c')
| -rw-r--r-- | nuttx/arch/arm/src/armv7-m/up_mpu.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/nuttx/arch/arm/src/armv7-m/up_mpu.c b/nuttx/arch/arm/src/armv7-m/up_mpu.c new file mode 100644 index 000000000..27936562c --- /dev/null +++ b/nuttx/arch/arm/src/armv7-m/up_mpu.c @@ -0,0 +1,176 @@ +/**************************************************************************** + * arch/arm/src/armv7-m/up_mpu.c + * + * Copyright (C) 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * 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]; +} + + + |