/* Get bus(which USART mounts on) clock frequency value.  */
static uint32_t USART_GetBusClockFreq(const CM_USART_TypeDef *USARTx)
/* Get bus(which USART mounts on) clock frequency value.  */
static uint32_t USART_GetBusClockFreq(const CM_USART_TypeDef *USARTx)
{
    uint32_t u32BusClock;
    (void)USARTx;
    u32BusClock = SystemCoreClock >> (READ_REG32_BIT(CM_CMU->SCFGR, CMU_SCFGR_PCLK1S) >> CMU_SCFGR_PCLK1S_POS);
    return u32BusClock;
}