UART_ACR_TXDIS
up->acr |= UART_ACR_TXDIS;
if (port->type == PORT_16C950 && up->acr & UART_ACR_TXDIS) {
up->acr &= ~UART_ACR_TXDIS;
up->acr |= UART_ACR_TXDIS;
if (up->port.type == PORT_16C950 && up->acr & UART_ACR_TXDIS) {
up->acr &= ~UART_ACR_TXDIS;