1. GR551x系列不支持寄存器方式查询复位原因，SDK ≥V1.7.0版本提供如下接口判断是否看门狗复位。但是这个标志在platform_init里面被ll_pwr_clear_wakeup_event(LL_PWR_WKUP_EVENT_ALL)清除了，导致不能判断是否是aon wdt复位，因此需要在清除前保存标志。

/**
  * @brief  Indicate if the AON WDT Reboot Event Flag is set or not.
  * @note   This bit is set by hardware when the counter has reached alarm value.
  *         It can be cleared by writing 0 to this bit.
  *
  *  \rst
  *  +----------------------+-----------------------------------+
  *  | Register             | BitsName                          |
  *  +======================+===================================+
  *  | SLP_EVENT            | SLP_EVENT_WDT                     |
  *  +----------------------+-----------------------------------+
  * \endrst
  *
  * @retval State of bit (1 or 0).
  */
__STATIC_INLINE uint32_t ll_aon_wdt_is_active_flag_reboot(void)
{
    return (uint32_t)(READ_BITS(AON->SLP_EVENT, AON_SLP_EVENT_WDT_REBOOT) == AON_SLP_EVENT_WDT_REBOOT);
}

使用示例如下：

uint32_t wdt_is_active = 0;
void platform_init(void)
{
    wdt_is_active = ll_aon_wdt_is_active_flag_reboot();
    /* if BLE not fully power off, reset and power off it manually */
    if((AON->PWR_RET01 & AON_PWR_REG01_PWR_EN_PD_COMM_TIMER) || \
       (AON->PWR_RET01 & AON_PWR_REG01_PWR_EN_PD_COMM_CORE))
       ......
}

2. GR5525/GR5526/GR5332支持寄存器方式查询复位状态，以GR5525为例，参考datasheet 3.4.5.1章节介绍。

目前SDK还未提供对应的API查询复位原因，可以参考如下方法接口：

uint8_t sys_device_reset_season(void)
{
    uint8_t reset_season = AON_CTL->DBG_REG_RST_SRC & 0x0F;

    if (reset_season)
    {
        AON_CTL->DBG_REG_RST_SRC = (1 << 24) | (1 << 25) | (1 << 31);
        while (AON_CTL->DBG_REG_RST_SRC & (1 << 30));
        delay_us(100);
    
    }

    AON_CTL->DBG_REG_RST_SRC = (1 << 24) | (1 << 31);
    while ((AON_CTL->DBG_REG_RST_SRC & (1 << 30)) || !(AON_CTL->DBG_REG_RST_SRC & ( 1 << 16)));
    delay_us(100);

    return reset_season;
}

PS：GR533x复位原因寄存器参考datasheet 3.4.5.1章节；GR5526x复位原因寄存器参考datasheet 5.5章节介绍。