LCR_DLAB
udbg_uart_out(UART_LCR, LCR_DLAB);
udbg_uart_out(UART_LCR, old_lcr | LCR_DLAB);
outb(LCR_DLAB | LCR_BIT5, LCR(iobase));
outb(LCR_DLAB | LCR_BIT8, LCR(dev->base_addr));