STM32看门狗启动后系统不能复位

我们从bsp\stm32f429-disco移植了bsp，写了下面的代码调用Libraries/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_iwdg.c中的HAL_IWDG_Init、HAL_IWDG_Refresh
```rt_uint8_t IWDG_Init(rt_uint8_t pre, rt_uint16_t rlr) {
IWDG_TypeDef hiwdg_type;
hiwdg.Instance = &hiwdg_type;

hiwdg.Init.Prescaler = pre;    
hiwdg.Init.Reload = rlr;
if(HAL_IWDG_Init(&hiwdg) == HAL_OK){
   return 1;
}else{
   return 0;
}

}

/ 喂狗
*/
rt_uint8_t IWDG_Feed(void) {
if(HAL_IWDG_Refresh(&hiwdg) == HAL_OK){
return 1;
}else{
return 0;
}
}
```
测试发现HAL_IWDG_Init返回了HAL_OK，在没有调用IWDG_Feed喂狗的情况下，MCU也不会复位，会是什么原因？