在u-boot中实现UART3驱动

/*
 * Copyright (C) 2010 ZLGMCU
 * All rights reserved.
 *
 * @Author: Chenxibing
 * @Descr: LPC3250 UART5 & UART3 driver for AnyWhere.
 */
#include <common.h>
#include <lpc3250.h>

DECLARE_GLOBAL_DATA_PTR;

初始化，波特率9600，8N1。
int uart3_init(void)
{
    int tmp32;

    CLKPWR->clkpwr_uart_clk_ctrl |= CLKPWR_UARTCLKCTRL_UART3_EN;
    CLKPWR->clkpwr_uart3_clk_ctrl = (254<<0)|(3<<8); //9600

    UARTCNTL->ctrl &= (~_BIT(11));
    UARTCNTL->clkmode |= (UART_CLKMODE_ON << 4);

    UART3->lcr |= UART_LCR_DIVLATCH_EN;
    UART3->dlm_ier = 0x00;
    UART3->dll_fifo = 0x01;
    UART3->lcr = UART_LCR_WLEN_8BITS;

    //UART3->iir_fcr = (0x0F | (0x03<<6));

    /* Clear FIFOs and set FIFO level */
    UART3->iir_fcr = (UART_FCR_RXFIFO_TL16 |
        UART_FCR_TXFIFO_TL0 | UART_FCR_FIFO_CTRL |
        UART_FCR_FIFO_EN | UART_FCR_TXFIFO_FLUSH |
        UART_FCR_RXFIFO_FLUSH);

    UART3->dlm_ier = 0; //disable interrupt


    tmp32 = UART3->iir_fcr;
    tmp32 = UART3->lsr;

    return 0;
}

采用查询方式读取一个字节：
unsigned char uart3_read_byte(void)
{
    /* Wait for a character from the UART */
    while ((UART3->lsr & UART_LSR_RDR) == 0);

    return (int) (UART3->dll_fifo & 0xFF);
}

发送一个字节，等待发送完毕：
void uart3_write_byte(unsigned char c)
{
    /* Wait for FIFO to become empty */
    while ((UART3->lsr & UART_LSR_THRE) == 0);

    UART3->dll_fifo = (u32) c;
}

通过UART3发送字符串：
void uart3_write_str(unsigned char *s, int len)
{
    int i;

    for(i=0; i<len; i++) {
        uart3_write_byte(*s);
        s++;
    }
}

#define DPRINTK(nlevel, klevel, fmt, args...)       ((void)((NETIF_MSG_##nlevel & pdata->msg_enable) &&  printk(KERN_##klevel "%s: %s: " fmt "\n", pdata->dev->name, __func__, ## args)))