portapack-mayhem/firmware/application/m4_startup.cpp

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/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "m4_startup.hpp"
#include "hal.h"
#include <cstdint>
#include <cstddef>
#include <cstring>
static constexpr uint32_t m4_text_flash_image_offset = 0x20000;
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static constexpr size_t m4_text_size = 0x8000;
static constexpr uint32_t m4_text_flash_base = LPC_SPIFI_DATA_CACHED_BASE + m4_text_flash_image_offset;
static constexpr uint32_t m4_text_ram_base = 0x10080000;
/* TODO: OK, this is cool, but how do I put the M4 to sleep so I can switch to
* a different image? Other than asking the old image to sleep while the M0
* makes changes?
*
* I suppose I could force M4MEMMAP to an invalid memory reason which would
* cause an exception and effectively halt the M4. But that feels gross.
*/
void m4_init() {
/* Initialize M4 code RAM */
std::memcpy((void*)m4_text_ram_base, (void*)m4_text_flash_base, m4_text_size);
/* M4 core is assumed to be sleeping with interrupts off, so we can mess
* with its address space and RAM without concern.
*/
LPC_CREG->M4MEMMAP = m4_text_ram_base;
/* Reset M4 core */
LPC_RGU->RESET_CTRL[0] = (1 << 13);
}