AML_UART_WFIFO
writel(port->x_char, port->membase + AML_UART_WFIFO);
writel(ch, port->membase + AML_UART_WFIFO);
writel(c, port->membase + AML_UART_WFIFO);
writel(ch, port->membase + AML_UART_WFIFO);