Viewing file:  ip32-timer.c (1.33 KB) -rw-r--r--
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/*
* IP32 timer calibration
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2001 Keith M Wesolowski
*/
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <asm/mipsregs.h>
#include <asm/param.h>
#include <asm/ip32/crime.h>
#include <asm/ip32/ip32_ints.h>
extern u32 cc_interval;
/* An arbitrary time; this can be decreased if reliability looks good */
#define WAIT_MS 10
#define PER_MHZ (1000000 / 2 / HZ)
void __init ip32_timer_setup (struct irqaction *irq) {
u64 crime_time;
u32 cc_tick;
printk("Calibrating system timer... ");
crime_time = crime_read_64 (CRIME_TIME) & CRIME_TIME_MASK;
cc_tick = read_32bit_cp0_register (CP0_COUNT);
while ((crime_read_64 (CRIME_TIME) & CRIME_TIME_MASK) - crime_time
< WAIT_MS * 1000000 / CRIME_NS_PER_TICK)
;
cc_tick = read_32bit_cp0_register (CP0_COUNT) - cc_tick;
cc_interval = cc_tick / HZ * (1000 / WAIT_MS);
/* The round-off seems unnecessary; in testing, the error of the
* above procedure is < 100 ticks, which means it gets filtered
* out by the HZ adjustment.
*/
cc_interval = (cc_interval / PER_MHZ) * PER_MHZ;
printk("%d MHz CPU detected\n", (int) (cc_interval / PER_MHZ));
setup_irq (CLOCK_IRQ, irq);
}
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