text: // Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
  //
  // 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 "sdkconfig.h"
  #include <string.h>
  #include "esp_system.h"
  #include "internal/esp_system_internal.h"
  #include "esp8266/rtc_register.h"
  #include "esp8266/rom_functions.h"
  #include "esp_log.h"
  #include "esp_libc.h"
  
  #define RTC_RESET_SW_CAUSE_REG              RTC_STORE0
  #define RTC_RESET_HW_CAUSE_REG              RTC_STATE1
  #define RTC_WAKEUP_HW_CAUSE_REG             RTC_STATE2
  
  #define RTC_RESET_HW_CAUSE_LSB              0
  #define RTC_RESET_HW_CAUSE_MSB              3
  
  #define RTC_WAKEUP_HW_CAUSE_LSB             8
  #define RTC_WAKEUP_HW_CAUSE_MSB             13
  
  static const char *TAG = "reset_reason";
  static uint32_t s_reset_reason;
  
  static inline void esp_reset_reason_clear_hint()
  {
      rtc_sys_info.hint = 0;
  }
  
  static inline uint32_t esp_reset_reason_get_hint(uint32_t hw_reset)
  {
      if (hw_reset == POWERON_RESET && ((rtc_sys_info.hint != ESP_RST_SW) && (rtc_sys_info.hint != ESP_RST_FAST_SW)))
          rtc_sys_info.hint = 0;
  
      return rtc_sys_info.hint;
  }
  
  static inline uint32_t esp_rtc_get_reset_reason(void)
  {
      return GET_PERI_REG_BITS(RTC_RESET_HW_CAUSE_REG, RTC_RESET_HW_CAUSE_MSB, RTC_RESET_HW_CAUSE_LSB);
  }
  
  #if CONFIG_RESET_REASON_CHECK_WAKEUP
  static inline uint32_t esp_rtc_get_wakeup_reason(void)
  {
      return GET_PERI_REG_BITS(RTC_WAKEUP_HW_CAUSE_REG, RTC_WAKEUP_HW_CAUSE_MSB, RTC_WAKEUP_HW_CAUSE_LSB);
  }
  #endif
  
  static inline uint32_t get_reset_reason(uint32_t rtc_reset_reason, uint32_t reset_reason_hint)
  {
      switch (rtc_reset_reason) {
          case POWERON_RESET:
              if (reset_reason_hint == ESP_RST_SW ||
                  reset_reason_hint == ESP_RST_FAST_SW)
                  return reset_reason_hint;
              return ESP_RST_POWERON;
          case EXT_RESET:
              if (reset_reason_hint == ESP_RST_DEEPSLEEP) {
                  return reset_reason_hint;
              }
              return ESP_RST_EXT;
          case SW_RESET:
              if (reset_reason_hint == ESP_RST_PANIC ||
                  reset_reason_hint == ESP_RST_BROWNOUT ||
                  reset_reason_hint == ESP_RST_TASK_WDT) {
                  return reset_reason_hint;
              }
              return ESP_RST_SW;
          case DEEPSLEEP_RESET:
              return ESP_RST_DEEPSLEEP;
          case OWDT_RESET:
              return ESP_RST_WDT;
          case SDIO_RESET:
              return ESP_RST_SDIO;
          default:
              return ESP_RST_UNKNOWN;
      }
  }
  
  /**
   * Internal function to initialize SoC reset reason at system initialization
   */
  static void __esp_reset_reason_init(int init)
  {
      const uint32_t hw_reset = esp_rtc_get_reset_reason();
  #if CONFIG_RESET_REASON_CHECK_WAKEUP
      const uint32_t hw_wakeup = esp_rtc_get_wakeup_reason();
  #else
      const uint32_t hw_wakeup = 0;
  #endif
      const uint32_t hint = esp_reset_reason_get_hint(hw_reset);
  
      s_reset_reason = get_reset_reason(hw_reset, hint);
      if (init && hint != ESP_RST_UNKNOWN) {
          esp_reset_reason_clear_hint();
      }
  
      if (init)
          ESP_LOGD(TAG, "RTC reset %u wakeup %u store %u, reason is %u", hw_reset, hw_wakeup, hint, s_reset_reason);
  }
  
  /**
   * @brief  Internal function to get SoC reset reason at system initialization
   */
  void esp_reset_reason_init(void)
  {
      __esp_reset_reason_init(1);
  }
  
  #if CONFIG_RESET_REASON
  
  /**
   * @brief  Internal function to set reset reason hint
   */
  void esp_reset_reason_set_hint(esp_reset_reason_t hint)
  {
      rtc_sys_info.hint = hint;
  }
  
  /**
   * @brief  Get reason of last reset
   */
  esp_reset_reason_t esp_reset_reason(void)
  {
      return (esp_reset_reason_t)s_reset_reason;
  }
  
  #else /* CONFIG_RESET_REASON */
  
  /**
   * null function for pass compiling
   */
  void esp_reset_reason_set_hint(esp_reset_reason_t hint)
  {
  
  }
  
  #endif /* CONFIG_RESET_REASON */
  
  /**
   * Get reason of last reset but not clear it for next reset
   */
  esp_reset_reason_t esp_reset_reason_early(void)
  {
      __esp_reset_reason_init(0);
  
      return (esp_reset_reason_t)s_reset_reason;
  }
  