sw/device/boot_rom/boot_rom.c

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

#include "sw/device/boot_rom/bootstrap.h"
#include "sw/device/boot_rom/chip_info.h"  // Generated.
#include "sw/device/lib/arch/device.h"
#include "sw/device/lib/base/mmio.h"
#include "sw/device/lib/common.h"
#include "sw/device/lib/dif/dif_gpio.h"
#include "sw/device/lib/pinmux.h"
#include "sw/device/lib/runtime/log.h"
#include "sw/device/lib/runtime/print.h"
#include "sw/device/lib/testing/test_status.h"
#include "sw/device/lib/uart.h"

/**
 * This symbol is defined in sw/device/boot_rom/rom_link.ld,
 * and describes the location of the flash header.
 *
 * The actual contents are not defined by the ROM, but rather
 * by the flash binary: see sw/device/exts/common/flash_link.ld
 * for that.
 */
extern struct { void (*entry)(void); } _flash_header;

void _boot_start(void) {
  test_status_set(kTestStatusInBootRom);
  pinmux_init();
  uart_init(kUartBaudrate);
  base_set_stdout(uart_stdout);

  LOG_INFO("%s", chip_info);

  int bootstrap_err = bootstrap();
  if (bootstrap_err != 0) {
    LOG_ERROR("Bootstrap failed with status code: %d", bootstrap_err);
    // Currently the only way to recover is by a hard reset.
    test_status_set(kTestStatusFailed);
  }

  LOG_INFO("Boot ROM initialisation has completed, jump into flash!");

  // Jump into flash. At this point, the contents of the flash binary have been
  // verified, and we can transfer control directly to it. It is the
  // flash binary's responsibily to set up its own stack, and to never
  // return.
  _flash_header.entry();

  // If there's a stop address, write to it.
  if (kDeviceStopAddress != 0) {
    mmio_region_t end_sim_addr = mmio_region_from_addr(kDeviceStopAddress);
    // We write `0xFFFFFFFE` to differentiate from `abort` (which writes
    // `0xFFFFFFFF`), and the `main` function in the flash image (which is
    // likely to return `0x0` or `0x1` to match unix exit codes).
    mmio_region_write32(end_sim_addr, 0x0, 0xFFFFFFFE);
  }
}