serial.c

Linux2.4.27在AT91RM9200下的U-BOOT代码。可以在Redhat9等版本下使用。适合ARM学习者使用。

/*
 * (C) Copyright 2004
 * METER Chen
 * http://www.cmtekchina.com
 * mailto:[e-mail]
 *
 * (C) Copyright 2002-2004
 * Wolfgang Denk, DENX Software Engineering, <[e-mail]>
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Marius Groeger <[e-mail]>
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Alex Zuepke <[e-mail]>
 *
 * Copyright (C) 1999 2000 2001 Erik Mouw ([e-mail])
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <common.h>
#include <asm/hardware.h>

#define	USTAT_RCV_READY         0x20   /* receive data ready */ 
#define	USTAT_TXB_EMPTY         0x40   /* tx buffer empty */

/* flush serial input queue. returns 0 on success or negative error
 * number otherwise
 */
static int serial_flush_input(void)
{
	volatile u32 tmp;

	/* keep on reading as long as the receiver is not empty */
	while(UARTSTAT0 & USTAT_RCV_READY) {
		tmp = UARTRXB0;
	}

	return 0;
}


/* flush output queue. returns 0 on success or negative error number
 * otherwise
 */
static int serial_flush_output(void)
{
	/* wait until the transmitter is no longer busy */
	while(!(UARTSTAT0 & USTAT_TXB_EMPTY)) {
	}

	return 0;
}


void serial_setbrg (void)
{
	DECLARE_GLOBAL_DATA_PTR;

	u32 divisor = 0;

	/* get correct divisor */
	switch(gd->baudrate) {

	case 1200:
		divisor = (1301<<4);
		break;

	case 9600:
		divisor = (162<<4);
		break;

	case 19200:
		divisor = (80<<4);
		break;

	case 38400:
		divisor = (40<<4);
		break;

	case 57600:
		divisor = (26<<4);
		break;		

	case 115200:
		divisor = (13<<4);
		break;
	}

	serial_flush_output();
	serial_flush_input();
	
	UARTLCON0 = 0x03;
        UARTCONT0 = 0x09;
        UARTBRD0  = divisor;
	
	UARTLCON1 = 0x03;
        UARTCONT1 = 0x09;
        UARTBRD1  = divisor;

	for(divisor=0; divisor<100; divisor++) {
		/* NOP */
	}
}


/*
 * Initialise the serial port with the given baudrate. The settings
 * are always 8 data bits, no parity, 1 stop bit, no start bits.
 *
 */
int serial_init (void)
{
	serial_setbrg();

	return (0);
}


/*
 * Output a single byte to the serial port.
 */
void serial_putc (const char c)
{
	/* wait for room in the transmit FIFO */
	while(!(UARTSTAT0 & USTAT_TXB_EMPTY));

	UARTTXH0 = (unsigned char)c;

	/*
		to be polite with serial console add a line feed
		to the carriage return character
	*/
	if (c=='\n')
		serial_putc('\r');
}

/*
 * Read a single byte from the serial port. Returns 1 on success, 0
 * otherwise. When the function is succesfull, the character read is
 * written into its argument c.
 */
int serial_tstc (void)
{
	return (UARTSTAT0 & USTAT_RCV_READY);
}

/*
 * Read a single byte from the serial port. Returns 1 on success, 0
 * otherwise. When the function is succesfull, the character read is
 * written into its argument c.
 */
int serial_getc (void)
{
	int rv;

	for(;;) {
		rv = serial_tstc();

		if(rv > 0)
			return UARTRXB0;
	}
}

void
serial_puts (const char *s)
{
	while (*s) {
		serial_putc (*s++);
	}
}