pebble/platform/silk/boot/src/drivers/flash/mx25u.c

/*
 * Copyright 2024 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdbool.h>
#include <stdint.h>

#include "board/board.h"
#include "drivers/flash.h"
#include "drivers/gpio.h"
#include "drivers/periph_config.h"
#include "util/delay.h"

#include "stm32f4xx_gpio.h"
#include "stm32f4xx_qspi.h"

#define MX25U_FASTREAD_DUMMYCYCLES 4

typedef enum MX25UCommand {
  // SPI/QSPI Commands
  MX25UCommand_FastRead = 0x0B,         // FAST_READ
  MX25UCommand_QSPIEnable = 0x35,       // QPI
  MX25UCommand_ResetEnable = 0x66,      // RSTEN
  MX25UCommand_Reset = 0x99,            // RST

  // QSPI only commands
  MX25UCommand_QSPI_ID = 0xAF,        // QPIID
} MX25UCommand;

// Helpful Enums
typedef enum {
  QSPIFlag_Retain = 0,
  QSPIFlag_ClearTC = 1,
} QSPIFlag;

static void prv_enable_qspi_clock(void) {
  periph_config_enable(RCC_AHB3PeriphClockCmd, RCC_AHB3Periph_QSPI);
}

static void prv_disable_qspi_clock(void) {
  periph_config_disable(RCC_AHB3PeriphClockCmd, RCC_AHB3Periph_QSPI);
}

static void prv_set_num_data_bytes(uint32_t length) {
  // From the docs: QSPI_DataLength: Number of data to be retrieved, value+1.
  // so 0 is 1 byte, so we substract 1 from the length. -1 is read the entire flash length.
  QSPI_SetDataLength(length - 1);
}

static void prv_wait_for_qspi_transfer_complete(QSPIFlag actions) {
  while (QSPI_GetFlagStatus(QSPI_FLAG_TC) == RESET) { }

  if (actions == QSPIFlag_ClearTC) {
    QSPI_ClearFlag(QSPI_FLAG_TC);
  }
}

static void prv_wait_for_qspi_not_busy(void) {
  while (QSPI_GetFlagStatus(QSPI_FLAG_BUSY) != RESET) { }
}

static void prv_quad_enable() {
  QSPI_ComConfig_InitTypeDef qspi_com_config;
  QSPI_ComConfig_StructInit(&qspi_com_config);
  qspi_com_config.QSPI_ComConfig_FMode = QSPI_ComConfig_FMode_Indirect_Write;
  qspi_com_config.QSPI_ComConfig_IMode = QSPI_ComConfig_IMode_1Line;
  qspi_com_config.QSPI_ComConfig_Ins = MX25UCommand_QSPIEnable;
  QSPI_ComConfig_Init(&qspi_com_config);

  prv_wait_for_qspi_transfer_complete(QSPIFlag_ClearTC);

  prv_wait_for_qspi_not_busy();
}

static void prv_flash_reset(void) {
  QSPI_ComConfig_InitTypeDef qspi_com_config;
  QSPI_ComConfig_StructInit(&qspi_com_config);
  qspi_com_config.QSPI_ComConfig_FMode = QSPI_ComConfig_FMode_Indirect_Write;
  qspi_com_config.QSPI_ComConfig_IMode = QSPI_ComConfig_IMode_4Line;
  qspi_com_config.QSPI_ComConfig_Ins = MX25UCommand_ResetEnable;
  QSPI_ComConfig_Init(&qspi_com_config);

  prv_wait_for_qspi_transfer_complete(QSPIFlag_ClearTC);

  QSPI_ComConfig_StructInit(&qspi_com_config);
  qspi_com_config.QSPI_ComConfig_FMode = QSPI_ComConfig_FMode_Indirect_Write;
  qspi_com_config.QSPI_ComConfig_IMode = QSPI_ComConfig_IMode_4Line;
  qspi_com_config.QSPI_ComConfig_Ins = MX25UCommand_Reset;
  QSPI_ComConfig_Init(&qspi_com_config);

  prv_wait_for_qspi_transfer_complete(QSPIFlag_ClearTC);

  delay_us(12000); // 12ms reset if busy with an erase!

  // Return the flash to Quad SPI mode, all our commands are quad-spi and it'll just cause
  // problems/bugs for someone if it comes back in single spi mode
  prv_quad_enable();
}

static bool prv_flash_check_whoami(void) {
  const unsigned int num_whoami_bytes = 3;

  prv_set_num_data_bytes(num_whoami_bytes);

  QSPI_ComConfig_InitTypeDef qspi_com_config;
  QSPI_ComConfig_StructInit(&qspi_com_config);
  qspi_com_config.QSPI_ComConfig_FMode = QSPI_ComConfig_FMode_Indirect_Read;
  qspi_com_config.QSPI_ComConfig_DMode = QSPI_ComConfig_DMode_4Line;
  qspi_com_config.QSPI_ComConfig_IMode = QSPI_ComConfig_IMode_4Line;
  qspi_com_config.QSPI_ComConfig_Ins = MX25UCommand_QSPI_ID;
  QSPI_ComConfig_Init(&qspi_com_config);

  prv_wait_for_qspi_transfer_complete(QSPIFlag_ClearTC);

  uint32_t read_whoami = 0;
  for (unsigned int i = 0; i < num_whoami_bytes; ++i) {
    read_whoami |= QSPI_ReceiveData8() << (8 * i);
  }

  prv_wait_for_qspi_not_busy();

  const uint32_t expected_whoami = 0x3725c2;
  if (read_whoami == expected_whoami) {
    return true;
  } else {
    return false;
  }
}

void flash_init(void) {
  prv_enable_qspi_clock();
  // init GPIOs
  for (unsigned i = 0; i < QSpiPinCount; ++i) {
    gpio_af_init(&BOARD_CONFIG_FLASH_PINS[i], GPIO_OType_PP, GPIO_Speed_100MHz, GPIO_PuPd_NOPULL);
  }

  // Init QSPI peripheral
  QSPI_InitTypeDef qspi_config;
  QSPI_StructInit(&qspi_config);
  qspi_config.QSPI_SShift = QSPI_SShift_HalfCycleShift;
  qspi_config.QSPI_Prescaler = 0x0;
  qspi_config.QSPI_CKMode = QSPI_CKMode_Mode0;
  qspi_config.QSPI_CSHTime = QSPI_CSHTime_1Cycle;
  qspi_config.QSPI_FSize = 22; // 2^23 = 8MB. -> 23 - 1 = 22
  qspi_config.QSPI_FSelect = QSPI_FSelect_1;
  qspi_config.QSPI_DFlash = QSPI_DFlash_Disable;
  QSPI_Init(&qspi_config);

  QSPI_Cmd(ENABLE);

  // Must call quad_enable first, all commands are QSPI
  prv_quad_enable();

  // Reset the flash to stop any program's or erase in progress from before reboot
  prv_flash_reset();

  prv_disable_qspi_clock();
}

bool flash_sanity_check(void) {
  prv_enable_qspi_clock();

  bool result = prv_flash_check_whoami();

  prv_disable_qspi_clock();

  return result;
}

void flash_read_bytes(uint8_t *buffer_ptr, uint32_t start_addr, uint32_t buffer_size) {
  prv_enable_qspi_clock();

  prv_set_num_data_bytes(buffer_size);

  QSPI_ComConfig_InitTypeDef qspi_com_config;
  QSPI_ComConfig_StructInit(&qspi_com_config);
  qspi_com_config.QSPI_ComConfig_FMode = QSPI_ComConfig_FMode_Indirect_Read;
  qspi_com_config.QSPI_ComConfig_DMode = QSPI_ComConfig_DMode_4Line;
  qspi_com_config.QSPI_ComConfig_DummyCycles = MX25U_FASTREAD_DUMMYCYCLES;
  qspi_com_config.QSPI_ComConfig_ADMode = QSPI_ComConfig_ADMode_4Line;
  qspi_com_config.QSPI_ComConfig_IMode = QSPI_ComConfig_IMode_4Line;
  qspi_com_config.QSPI_ComConfig_ADSize = QSPI_ComConfig_ADSize_24bit;
  qspi_com_config.QSPI_ComConfig_Ins = MX25UCommand_FastRead;
  QSPI_ComConfig_Init(&qspi_com_config);

  QSPI_SetAddress(start_addr);

  uint8_t *write_ptr = buffer_ptr;
  for (unsigned i = 0; i < buffer_size; ++i) {
    write_ptr[i] = QSPI_ReceiveData8();
  }

  QSPI_ClearFlag(QSPI_FLAG_TC);
  prv_wait_for_qspi_not_busy();

  prv_disable_qspi_clock();
}