1/*
2 *  8250/16550-type serial ports prom_putchar()
3 *
4 *  Copyright (C) 2010  Yoichi Yuasa <yuasa@linux-mips.org>
5 *
6 *  This program is free software; you can redistribute it and/or modify
7 *  it under the terms of the GNU General Public License as published by
8 *  the Free Software Foundation; either version 2 of the License, or
9 *  (at your option) any later version.
10 *
11 *  This program is distributed in the hope that it will be useful,
12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 *  GNU General Public License for more details.
15 *
16 *  You should have received a copy of the GNU General Public License
17 *  along with this program; if not, write to the Free Software
18 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20#include <linux/io.h>
21#include <linux/serial_core.h>
22#include <linux/serial_reg.h>
23
24static void __iomem *serial8250_base;
25static unsigned int serial8250_reg_shift;
26static unsigned int serial8250_tx_timeout;
27
28void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift,
29				  unsigned int timeout)
30{
31	serial8250_base = (void __iomem *)base;
32	serial8250_reg_shift = reg_shift;
33	serial8250_tx_timeout = timeout;
34}
35
36static inline u8 serial_in(int offset)
37{
38	return readb(serial8250_base + (offset << serial8250_reg_shift));
39}
40
41static inline void serial_out(int offset, char value)
42{
43	writeb(value, serial8250_base + (offset << serial8250_reg_shift));
44}
45
46void prom_putchar(char c)
47{
48	unsigned int timeout;
49	int status, bits;
50
51	if (!serial8250_base)
52		return;
53
54	timeout = serial8250_tx_timeout;
55	bits = UART_LSR_TEMT | UART_LSR_THRE;
56
57	do {
58		status = serial_in(UART_LSR);
59
60		if (--timeout == 0)
61			break;
62	} while ((status & bits) != bits);
63
64	if (timeout)
65		serial_out(UART_TX, c);
66}
67