stm32 h747 uart8 hal_uart_init wrong

If when i use hal_uart_init(&huart8) get result Details:HAL_ERROR Default:HAL_ERROR，Decimal:1，Hex:0x1，Binary:1，Octal:01.When i use step into ，reach at final while（sets-- ！=0u）and no more what does this mean ？ how could i solve this problem？

static void MX_USART8_UART_Init(void)
{

/* USER CODE BEGIN USART1_Init 0 */

/* USER CODE END USART1_Init 0 */

/* USER CODE BEGIN USART1_Init 1 */

/* USER CODE END USART1_Init 1 */
huart8.Instance = UART8;
huart8.Init.BaudRate = 115200;
huart8.Init.WordLength = UART_WORDLENGTH_8B;
huart8.Init.StopBits = UART_STOPBITS_1;
huart8.Init.Parity = UART_PARITY_NONE;
huart8.Init.Mode = UART_MODE_TX_RX;
huart8.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart8.Init.OverSampling = UART_OVERSAMPLING_16;
huart8.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart8.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart8.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;

if (HAL_UART_Init(&huart8) != HAL_OK)
{
Error_Handler();
}