time.c

linux-2.6.15.6

/*
 *  linux/arch/m68k/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *
 * This file contains the m68k-specific time handling details.
 * Most of the stuff is located in the machine specific files.
 *
 * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
 *		"A Kernel Model for Precision Timekeeping" by Dave Mills
 */

#include <linux/config.h> /* CONFIG_HEARTBEAT */
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/rtc.h>

#include <asm/machdep.h>
#include <asm/io.h>

#include <linux/time.h>
#include <linux/timex.h>
#include <linux/profile.h>

static inline int set_rtc_mmss(unsigned long nowtime)
{
  if (mach_set_clock_mmss)
    return mach_set_clock_mmss (nowtime);
  return -1;
}

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "do_timer()" routine every clocktick
 */
static irqreturn_t timer_interrupt(int irq, void *dummy, struct pt_regs * regs)
{
	do_timer(regs);
#ifndef CONFIG_SMP
	update_process_times(user_mode(regs));
#endif
	profile_tick(CPU_PROFILING, regs);

#ifdef CONFIG_HEARTBEAT
	/* use power LED as a heartbeat instead -- much more useful
	   for debugging -- based on the version for PReP by Cort */
	/* acts like an actual heart beat -- ie thump-thump-pause... */
	if (mach_heartbeat) {
	    static unsigned cnt = 0, period = 0, dist = 0;

	    if (cnt == 0 || cnt == dist)
		mach_heartbeat( 1 );
	    else if (cnt == 7 || cnt == dist+7)
		mach_heartbeat( 0 );

	    if (++cnt > period) {
		cnt = 0;
		/* The hyperbolic function below modifies the heartbeat period
		 * length in dependency of the current (5min) load. It goes
		 * through the points f(0)=126, f(1)=86, f(5)=51,
		 * f(inf)->30. */
		period = ((672<<FSHIFT)/(5*avenrun[0]+(7<<FSHIFT))) + 30;
		dist = period / 4;
	    }
	}
#endif /* CONFIG_HEARTBEAT */
	return IRQ_HANDLED;
}

void time_init(void)
{
	struct rtc_time time;

	if (mach_hwclk) {
		mach_hwclk(0, &time);

		if ((time.tm_year += 1900) < 1970)
			time.tm_year += 100;
		xtime.tv_sec = mktime(time.tm_year, time.tm_mon, time.tm_mday,
				      time.tm_hour, time.tm_min, time.tm_sec);
		xtime.tv_nsec = 0;
	}
	wall_to_monotonic.tv_sec = -xtime.tv_sec;

	mach_sched_init(timer_interrupt);
}

/*
 * This version of gettimeofday has near microsecond resolution.
 */
void do_gettimeofday(struct timeval *tv)
{
	unsigned long flags;
	extern unsigned long wall_jiffies;
	unsigned long seq;
	unsigned long usec, sec, lost;
	unsigned long max_ntp_tick = tick_usec - tickadj;

	do {
		seq = read_seqbegin_irqsave(&xtime_lock, flags);

		usec = mach_gettimeoffset();
		lost = jiffies - wall_jiffies;

		/*
		 * If time_adjust is negative then NTP is slowing the clock
		 * so make sure not to go into next possible interval.
		 * Better to lose some accuracy than have time go backwards..
		 */
		if (unlikely(time_adjust < 0)) {
			usec = min(usec, max_ntp_tick);

			if (lost)
				usec += lost * max_ntp_tick;
		}
		else if (unlikely(lost))
			usec += lost * tick_usec;

		sec = xtime.tv_sec;
		usec += xtime.tv_nsec/1000;
	} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));


	while (usec >= 1000000) {
		usec -= 1000000;
		sec++;
	}

	tv->tv_sec = sec;
	tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);

int do_settimeofday(struct timespec *tv)
{
	time_t wtm_sec, sec = tv->tv_sec;
	long wtm_nsec, nsec = tv->tv_nsec;
	extern unsigned long wall_jiffies;

	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	write_seqlock_irq(&xtime_lock);
	/* This is revolting. We need to set the xtime.tv_nsec
	 * correctly. However, the value in this location is
	 * is value at the last tick.
	 * Discover what correction gettimeofday
	 * would have done, and then undo it!
	 */
	nsec -= 1000 * (mach_gettimeoffset() +
			(jiffies - wall_jiffies) * (1000000 / HZ));

	wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
	wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

	set_normalized_timespec(&xtime, sec, nsec);
	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

	ntp_clear();
	write_sequnlock_irq(&xtime_lock);
	clock_was_set();
	return 0;
}

EXPORT_SYMBOL(do_settimeofday);

/*
 * Scheduler clock - returns current time in ns units.
 */
unsigned long long sched_clock(void)
{
       return (unsigned long long)jiffies*(1000000000/HZ);
}