summaryrefslogtreecommitdiff
path: root/cpu/i386/timer.c
blob: 486d927a5a8a8c4cb5da7cbf220d0be91f4a3e05 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
/*
 * (C) Copyright 2002
 * Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * 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
 */

#include <common.h>
#include <asm/io.h>
#include <asm/i8254.h>
#include <asm/ibmpc.h>


static volatile unsigned long system_ticks;
static int timer_init_done =0;

static void timer_isr(void *unused)
{
	system_ticks++;
}

unsigned long get_system_ticks(void)
{
	return system_ticks;
}

#define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
#define TIMER2_VALUE 0x0a8e /* 440Hz */

int timer_init(void)
{
	system_ticks = 0;

	irq_install_handler(0, timer_isr, NULL);

	/* initialize timer 0 and 2
	 *
	 * Timer 0 is used to increment system_tick 1000 times/sec
	 * Timer 1 was used for DRAM refresh in early PC's
	 * Timer 2 is used to drive the speaker
	 * (to stasrt a beep: write 3 to port 0x61,
	 * to stop it again: write 0)
	 */

	outb(PIT_CMD_CTR0|PIT_CMD_BOTH|PIT_CMD_MODE2, PIT_BASE + PIT_COMMAND);
	outb(TIMER0_VALUE&0xff, PIT_BASE + PIT_T0);
	outb(TIMER0_VALUE>>8, PIT_BASE + PIT_T0);

	outb(PIT_CMD_CTR2|PIT_CMD_BOTH|PIT_CMD_MODE3, PIT_BASE + PIT_COMMAND);
	outb(TIMER2_VALUE&0xff, PIT_BASE + PIT_T2);
	outb(TIMER2_VALUE>>8, PIT_BASE + PIT_T2);

	timer_init_done = 1;

	return 0;
}


#ifdef CFG_TIMER_GENERIC

/* the unit for these is CFG_HZ */

/* FixMe: implement these */
void reset_timer (void)
{
	system_ticks = 0;
}

ulong get_timer (ulong base)
{
	return (system_ticks - base);
}

void set_timer (ulong t)
{
	system_ticks = t;
}

static u16 read_pit(void)
{
	u8 low;
	outb(PIT_CMD_LATCH, PIT_BASE + PIT_COMMAND);
	low = inb(PIT_BASE + PIT_T0);
	return ((inb(PIT_BASE + PIT_T0) << 8) | low);
}

/* this is not very exact */
void udelay (unsigned long usec)
{
	int counter;
	int wraps;

	if (!timer_init_done) {
		return;
	}
	counter = read_pit();
	wraps = usec/1000;
	usec = usec%1000;

	usec*=1194;
	usec/=1000;
	usec+=counter;
	if (usec > 1194) {
		usec-=1194;
		wraps++;
	}

	while (1) {
		int new_count = read_pit();

		if (((new_count < usec) && !wraps) || wraps < 0) {
			break;
		}

		if (new_count > counter) {
			wraps--;
		}
		counter = new_count;
	}

}

#if 0
/* this is a version with debug output */
void _udelay (unsigned long usec)
{
	int counter;
	int wraps;

	int usec1, usec2, usec3;
	int wraps1, wraps2, wraps3, wraps4;
	int ctr1, ctr2, ctr3, nct1, nct2;
	int i;
	usec1=usec;
	if (!timer_init_done) {
		return;
	}
	counter = read_pit();
	ctr1 = counter;
	wraps = usec/1000;
	usec = usec%1000;

	usec2 = usec;
	wraps1 = wraps;

	usec*=1194;
	usec/=1000;
	usec+=counter;
	if (usec > 1194) {
		usec-=1194;
		wraps++;
	}

	usec3 = usec;
	wraps2 = wraps;

	ctr2 = wraps3 = nct1 = 4711;
	ctr3 = wraps4 = nct2 = 4711;
	i=0;
	while (1) {
		int new_count = read_pit();
		i++;
		if ((new_count < usec && !wraps) || wraps < 0) {
			break;
		}

		if (new_count > counter) {
			wraps--;
		}
		if (ctr2==4711) {
			ctr2 = counter;
			wraps3 = wraps;
			nct1 = new_count;
		} else {
			ctr3 = counter;
			wraps4 = wraps;
			nct2 = new_count;
		}

		counter = new_count;
	}

	printf("udelay(%d)\n", usec1);
	printf("counter %d\n", ctr1);
	printf("1: wraps %d, usec %d\n", wraps1, usec2);
	printf("2: wraps %d, usec %d\n", wraps2, usec3);
	printf("new_count[0] %d counter %d wraps %d\n", nct1, ctr2, wraps3);
	printf("new_count[%d] %d counter %d wraps %d\n", i, nct2, ctr3, wraps4);

	printf("%d %d %d %d %d\n",
	       read_pit(), read_pit(), read_pit(),
	       read_pit(), read_pit());
}
#endif
#endif