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git.ipfire.org Git - people/ms/u-boot.git/blob - arch/x86/lib/pcat_timer.c
3 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
5 * See file CREDITS for list of people who contributed to this
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.
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.
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,
26 #include <asm/i8254.h>
27 #include <asm/ibmpc.h>
28 #include <asm/interrupt.h>
30 #define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
31 #define TIMER2_VALUE 0x0a8e /* 440Hz */
33 static int timer_init_done
;
37 /* initialize timer 0 and 2
39 * Timer 0 is used to increment system_tick 1000 times/sec
40 * Timer 1 was used for DRAM refresh in early PC's
41 * Timer 2 is used to drive the speaker
42 * (to start a beep: write 3 to port 0x61,
43 * to stop it again: write 0)
45 outb(PIT_CMD_CTR0
| PIT_CMD_BOTH
| PIT_CMD_MODE2
,
46 PIT_BASE
+ PIT_COMMAND
);
47 outb(TIMER0_VALUE
& 0xff, PIT_BASE
+ PIT_T0
);
48 outb(TIMER0_VALUE
>> 8, PIT_BASE
+ PIT_T0
);
50 outb(PIT_CMD_CTR2
| PIT_CMD_BOTH
| PIT_CMD_MODE3
,
51 PIT_BASE
+ PIT_COMMAND
);
52 outb(TIMER2_VALUE
& 0xff, PIT_BASE
+ PIT_T2
);
53 outb(TIMER2_VALUE
>> 8, PIT_BASE
+ PIT_T2
);
55 irq_install_handler(0, timer_isr
, NULL
);
63 static u16
read_pit(void)
67 outb(PIT_CMD_LATCH
, PIT_BASE
+ PIT_COMMAND
);
68 low
= inb(PIT_BASE
+ PIT_T0
);
70 return (inb(PIT_BASE
+ PIT_T0
) << 8) | low
;
73 /* this is not very exact */
74 void __udelay(unsigned long usec
)
79 if (timer_init_done
) {
94 int new_count
= read_pit();
96 if (((new_count
< usec
) && !wraps
) || wraps
< 0)
99 if (new_count
> counter
)