Linux Kernel  3.7.1
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early_printk.c
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1 /* early printk support
2  *
3  * Copyright (c) 2009 Philippe Vachon <[email protected]>
4  * Copyright (c) 2009 Lemote Inc.
5  * Author: Wu Zhangjin, [email protected]
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 
16 #define PORT(base, offset) (u8 *)(base + offset)
17 
18 static inline unsigned int serial_in(unsigned char *base, int offset)
19 {
20  return readb(PORT(base, offset));
21 }
22 
23 static inline void serial_out(unsigned char *base, int offset, int value)
24 {
25  writeb(value, PORT(base, offset));
26 }
27 
28 void prom_putchar(char c)
29 {
30  int timeout;
31  unsigned char *uart_base;
32 
33  uart_base = (unsigned char *)_loongson_uart_base;
34  timeout = 1024;
35 
36  while (((serial_in(uart_base, UART_LSR) & UART_LSR_THRE) == 0) &&
37  (timeout-- > 0))
38  ;
39 
40  serial_out(uart_base, UART_TX, c);
41 }