Function _uart_transmit

bsp/allwinner/libraries/drivers/drv_uart.c:723–786

}

static rt_ssize_t _uart_transmit(struct rt_serial_device *serial,
                                rt_uint8_t *buf, rt_size_t size, rt_uint32_t tx_flag)
{
    struct sunxi_uart *uart;
    size_t uart_base;

    uart = serial->parent.user_data;
    uart_base = SUNXI_UART0_BASE + uart->uart_port * 0x400;

    if (uart->uart_dma_flag & RT_DEVICE_FLAG_DMA_TX)
    {
        uint32_t remain = size;

        while (remain)
        {
            uint32_t write_count = 0;

            while (remain && (hal_readl(uart_base + UART_USR) & UART_USR_TFNF))
            {
                rt_uint8_t c = *buf++;
                hal_writeb(c, uart_base + UART_THR);
                remain--;
                write_count++;
            }

            while (write_count)
            {
                if (hal_readl(uart_base + UART_LSR) & UART_LSR_TEMT)
                {
                    break;
                }

                rt_completion_init(&(uart->tx_fifo_empty));
                uart_set_isr(uart->uart_port, 1, UART_IER_THRI);

                rt_err_t result = rt_completion_wait(&(uart->tx_fifo_empty), 100); // TODO: timeout calc by baud-rate.
                if (result == RT_EOK)
                {
                    break;
                }
            }
        }

        /* last byte, must wait TEMT(transmitter Empty). TODO: need delay? */
        while (1)
        {
            if (hal_readl(uart_base + UART_LSR) & UART_LSR_TEMT)
            {
                break;
            }
        }

        {
            struct rt_serial_tx_fifo *tx_fifo = RT_NULL;
            tx_fifo = (struct rt_serial_tx_fifo *)serial->serial_tx;
            tx_fifo->activated = RT_FALSE;
            rt_completion_done(&(tx_fifo->tx_cpt));
        }