UART_EFR_CTS
priv->efr |= UART_EFR_CTS;
efr |= UART_EFR_CTS;
up->efr |= UART_EFR_CTS;
up->efr &= ~(UART_EFR_CTS | UART_EFR_RTS);
serial_out(up, UART_EFR, cflag & CRTSCTS ? UART_EFR_CTS :0);