SPRD_RX_FIFO_CNT_MASK
while ((serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK) &&
while (timeout-- && serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK)
while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))