blob: e282f649acf6ea1f84e39075ea72632a04abfbaf [file] [log] [blame]
Graeme Russ8c63d472009-02-24 21:14:45 +11001/*
2 * (C) Copyright 2002
3 * Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
4 *
5 * See file CREDITS for list of people who contributed to this
6 * project.
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of
11 * the License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21 * MA 02111-1307 USA
22 */
23
24#include <common.h>
25#include <asm/io.h>
26#include <asm/i8254.h>
27#include <asm/ibmpc.h>
28
29#define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
30#define TIMER2_VALUE 0x0a8e /* 440Hz */
31
32int timer_init(void)
33{
34 /* initialize timer 0 and 2
35 *
36 * Timer 0 is used to increment system_tick 1000 times/sec
37 * Timer 1 was used for DRAM refresh in early PC's
38 * Timer 2 is used to drive the speaker
39 * (to stasrt a beep: write 3 to port 0x61,
40 * to stop it again: write 0)
41 */
42 outb (PIT_CMD_CTR0 | PIT_CMD_BOTH | PIT_CMD_MODE2,
43 PIT_BASE + PIT_COMMAND);
44 outb (TIMER0_VALUE & 0xff, PIT_BASE + PIT_T0);
45 outb (TIMER0_VALUE >> 8, PIT_BASE + PIT_T0);
46
47 outb (PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3,
48 PIT_BASE + PIT_COMMAND);
49 outb (TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2);
50 outb (TIMER2_VALUE >> 8, PIT_BASE + PIT_T2);
51
52 irq_install_handler (0, timer_isr, NULL);
53 unmask_irq (0);
54
55 return 0;
56}
57
58static u16 read_pit(void)
59{
60 u8 low;
61
62 outb (PIT_CMD_LATCH, PIT_BASE + PIT_COMMAND);
63 low = inb (PIT_BASE + PIT_T0);
64
65 return ((inb (PIT_BASE + PIT_T0) << 8) | low);
66}
67
68/* this is not very exact */
69void udelay (unsigned long usec)
70{
71 int counter;
72 int wraps;
73
74 if (timer_init_done)
75 {
76 counter = read_pit ();
77 wraps = usec / 1000;
78 usec = usec % 1000;
79
80 usec *= 1194;
81 usec /= 1000;
82 usec += counter;
83
84 while (usec > 1194) {
85 usec -= 1194;
86 wraps++;
87 }
88
89 while (1) {
90 int new_count = read_pit ();
91
92 if (((new_count < usec) && !wraps) || wraps < 0)
93 break;
94
95 if (new_count > counter)
96 wraps--;
97
98 counter = new_count;
99 }
100 }
101
102}