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/*
* arch/xtensa/kernel/time.c
*
* Timer and clock support.
*
* 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) 2005 Tensilica Inc.
*
* Chris Zankel <chris@zankel.net>
*/
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/profile.h>
#include <linux/delay.h>
#include <asm/timex.h>
#include <asm/platform.h>
#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
unsigned long ccount_per_jiffy; /* per 1/HZ */
unsigned long nsec_per_ccount; /* nsec per ccount increment */
#endif
static cycle_t ccount_read(void)
{
return (cycle_t)get_ccount();
}
static struct clocksource ccount_clocksource = {
.name = "ccount",
.rating = 200,
.read = ccount_read,
.mask = CLOCKSOURCE_MASK(32),
/*
* With a shift of 22 the lower limit of the cpu clock is
* 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than
* 2^10: Since we have 32 bits and the multiplicator can
* already take up as much as 10 bits, this leaves us with
* remaining upper 22 bits.
*/
.shift = 22,
};
static irqreturn_t timer_interrupt(int irq, void *dev_id);
static struct irqaction timer_irqaction = {
.handler = timer_interrupt,
.flags = IRQF_DISABLED,
.name = "timer",
};
void __init time_init(void)
{
xtime.tv_nsec = 0;
xtime.tv_sec = read_persistent_clock();
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
printk("Calibrating CPU frequency ");
platform_calibrate_ccount();
printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
(int)(ccount_per_jiffy/(10000/HZ))%100);
#endif
ccount_clocksource.mult =
clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
ccount_clocksource.shift);
clocksource_register(&ccount_clocksource);
/* Initialize the linux timer interrupt. */
setup_irq(LINUX_TIMER_INT, &timer_irqaction);
set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
}
/*
* The timer interrupt is called HZ times per second.
*/
irqreturn_t timer_interrupt (int irq, void *dev_id)
{
unsigned long next;
next = get_linux_timer();
again:
while ((signed long)(get_ccount() - next) > 0) {
profile_tick(CPU_PROFILING);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
write_seqlock(&xtime_lock);
do_timer(1); /* Linux handler in kernel/timer.c */
/* Note that writing CCOMPARE clears the interrupt. */
next += CCOUNT_PER_JIFFY;
set_linux_timer(next);
write_sequnlock(&xtime_lock);
}
/* Allow platform to do something useful (Wdog). */
platform_heartbeat();
/* Make sure we didn't miss any tick... */
if ((signed long)(get_ccount() - next) > 0)
goto again;
return IRQ_HANDLED;
}
#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
void __cpuinit calibrate_delay(void)
{
loops_per_jiffy = CCOUNT_PER_JIFFY;
printk("Calibrating delay loop (skipped)... "
"%lu.%02lu BogoMIPS preset\n",
loops_per_jiffy/(1000000/HZ),
(loops_per_jiffy/(10000/HZ)) % 100);
}
#endif
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