serial-s3c44b0.c

arm7,44b0芯片的blob程序,适用于学嵌入式linux的新手.

/*
 * serial-s3c44b0.c: StrongARM SA11x0 serial port driver
 *
 * Copyright (C) 2002  Erik Mouw <[e-mail]>
 *
 * $Id: serial-s3c44b0.c,v 1.2 2002/01/03 16:07:18 erikm Exp $
 *
 * 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
 *
 */

#ident "$Id: serial-s3c44b0.c,v 1.2 2002/01/03 16:07:18 erikm Exp $"

#ifdef HAVE_CONFIG_H
# include <blob/config.h>
#endif

#include <blob/arch.h>
#include <blob/errno.h>
#include <blob/serial.h>
#include <blob/types.h>




/* flush serial input queue. returns 0 on success or negative error
 * number otherwise
 */
static int s3c44b0_serial_flush_input(void)
{
	volatile u32 tmp;

	/* keep on reading as long as the receiver is not empty */
	while(REG(UTRSTAT0)&0x01) {
		tmp = REGB(URXH0);
	}

	return 0;
}




/* flush output queue. returns 0 on success or negative error number
 * otherwise
 */
static int s3c44b0_serial_flush_output(void)
{
	/* wait until the transmitter is no longer busy */
	while(!(REG(UTRSTAT0)&0x02)) {
	}

	return 0;
}




/* initialise serial port at the request baudrate. returns 0 on
 * success, or a negative error number otherwise
 */
static int s3c44b0_serial_init(serial_baud_t baud)
{
	u32 divisor;

	/* get correct divisor */
	switch(baud) {
	case baud_1200:
		divisor = 3124;
		break;

	case baud_9600:
		divisor = 390;
		break;

	case baud_19200:
		divisor = 194;
		break;

	case baud_38400:
		divisor = 97;
		break;

	case baud_57600:
		divisor = 64;
		break;

	case baud_115200:
		divisor = 32;
		break;

	default:
		return -ERANGE;
	}

	s3c44b0_serial_flush_output();
	REG(UFCON0) = 0x0;
	REG(ULCON0) = 0x03;
	REG(UCON0) = 0x05;
	REG(UBRDIV0) = divisor;

	REG(UFCON1) = 0x0;
	REG(ULCON1) = 0x03;
	REG(UCON1) = 0x05;
	REG(UBRDIV1) = divisor;

	for(divisor=0; divisor<100; divisor++);
	return 0;
}




/* check if there is a character available to read. returns 1 if there
 * is a character available, 0 if not, and negative error number on
 * failure */
static int s3c44b0_serial_poll(void)
{
	/* check for errors */
	if(REG(UERSTAT0)&0x07)
		return -ESERIAL;

	return (REG(UTRSTAT0)&0x01);
}




/* read one character from the serial port. return character (between
 * 0 and 255) on success, or negative error number on failure. this
 * function is blocking */
static int s3c44b0_serial_read(void)
{
	int rv;

	for(;;) {
		rv = s3c44b0_serial_poll();

		if(rv < 0)
			return rv;

		if(rv > 0)
			return REGB(URXH0);
	}
}




/* write character to serial port. return 0 on success, or negative
 * error number on failure. this function is blocking
 */
static int s3c44b0_serial_write(int c)
{
	/* wait for room in the transmit FIFO */
	while(!(REG(UTRSTAT0)&0x02));

	REGB(UTXH0) = (unsigned char)c;

	return 0;
}




/* export serial driver */
serial_driver_t s3c44b0_serial_driver = {
	init:		s3c44b0_serial_init,
	read:		s3c44b0_serial_read,
	write:		s3c44b0_serial_write,
	poll:		s3c44b0_serial_poll,
	flush_input:	s3c44b0_serial_flush_input,
	flush_output:	s3c44b0_serial_flush_output
};