early_printk.c revision db54ff246eae5acb6b7dffec2c05e682f91e0f4e 
1/*  early printk support
2 *
3 *  Copyright (c) 2009 Philippe Vachon <philippe@cowpig.ca>
4 *  Copyright (c) 2009 Lemote Inc.
5 *  Author: Wu Zhangjin, wuzj@lemote.com
6 *
7 *  This program is free software; you can redistribute  it and/or modify it
8 *  under  the terms of  the GNU General  Public License as published by the
9 *  Free Software Foundation;  either version 2 of the  License, or (at your
10 *  option) any later version.
11 */
12#include <linux/serial_reg.h>
13
14#include <loongson.h>
15#include <machine.h>
16
17#define PORT(base, offset) (u8 *)(base + offset)
18
19static inline unsigned int serial_in(unsigned char *base, int offset)
20{
21	return readb(PORT(base, offset));
22}
23
24static inline void serial_out(unsigned char *base, int offset, int value)
25{
26	writeb(value, PORT(base, offset));
27}
28
29void prom_putchar(char c)
30{
31	unsigned char *uart_base =
32		(unsigned char *) ioremap_nocache(LOONGSON_UART_BASE, 8);
33
34	while ((serial_in(uart_base, UART_LSR) & UART_LSR_THRE) == 0)
35		;
36
37	serial_out(uart_base, UART_TX, c);
38}
39