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/*
* (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>
#include <asm/interrupt.h>
#define TIMER0_VALUE 0x04aa /* 1kHz 1.9318MHz / 1000 */
#define TIMER2_VALUE 0x0a8e /* 440Hz */
static int timer_init_done = 0;
int timer_init(void)
{
/* 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);
irq_install_handler (0, timer_isr, NULL);
unmask_irq (0);
timer_init_done = 1;
return 0;
}
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)
{
counter = read_pit ();
wraps = usec / 1000;
usec = usec % 1000;
usec *= 1194;
usec /= 1000;
usec += counter;
while (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;
}
}
}
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