Function uart_irq_handler

bsp/allwinner/libraries/drivers/drv_uart.c:791–870

* this function will called when uart interrupt occur! */

 * this function will called when uart interrupt occur!
 */
static void uart_irq_handler(int vector, void *param)
{
    size_t uart_base;
    uint32_t iir, lsr;
    struct rt_serial_device *serial;
    struct sunxi_uart *uart;

    LOG_D("serial3:%p, uart3:%p\n", &serial3, &uart3);
    serial = (struct rt_serial_device *)param;
    uart = (struct sunxi_uart *)serial->parent.user_data;

    LOG_D("isr serial:%p, uart:%p, name:%s\n", serial, uart, serial->parent.parent.name);

    uart_base = SUNXI_UART0_BASE + uart->uart_port * 0x400;
    iir = hal_readb(uart_base + UART_IIR) & UART_IIR_IID_MASK;
    lsr = hal_readb(uart_base + UART_LSR);

    LOG_D("IRQ uart%d lsr is %08x \n", uart->uart_port, lsr);
    if (iir == UART_IIR_IID_BUSBSY)
    {
        (void)hal_readb(uart_base + UART_USR);

        /*
         * Before reseting lcr, we should ensure than uart is not in busy
         * state. Otherwise, a new busy interrupt will be introduced.
         * It is wise to set uart into loopback mode, since it can cut down the
         * serial in, then we should reset fifo(in my test, busy state
         * (UART_USR_BUSY) can't be cleard until the fifo is empty).
         */
        hal_writeb(hal_readb(uart_base + UART_MCR) | UART_MCR_LOOP, uart_base + UART_MCR);

        hal_writeb(UART_FCR_FIFO_EN, uart_base + UART_FCR);
        hal_writeb(UART_FCR_TXFIFO_RST | UART_FCR_RXFIFO_RST | UART_FCR_FIFO_EN, uart_base + UART_FCR);
        hal_writeb(0, uart_base + UART_FCR);

        uart_set_fifo(uart->uart_port);
        (void)hal_readb(uart_base + UART_FCR);

        hal_writeb(hal_readb(uart_base + UART_MCR) & ~UART_MCR_LOOP, uart_base + UART_MCR); /* exit loopback mode. */
    }
    else
    {
        if (lsr & (UART_LSR_DR | UART_LSR_BI))
        {
#ifdef RT_USING_SERIAL_V2
            struct rt_serial_rx_fifo *rx_fifo;
            uint8_t data;

            rx_fifo = (struct rt_serial_rx_fifo *)serial->serial_rx;
            RT_ASSERT(rx_fifo != RT_NULL);

            do
            {
                data = hal_readb(uart_base + UART_RBR);
                rt_ringbuffer_putchar(&(rx_fifo->rb), data);
                lsr = hal_readb(uart_base + UART_LSR);
            } while (lsr & UART_LSR_DR);