OWL_UART_STAT_TFFU
!(owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU),
!(reg & OWL_UART_STAT_TFFU),
while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)