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time.c

/*
 *  linux/arch/m68knommu/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/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/profile.h>
#include <linux/time.h>
#include <linux/timex.h>

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

#define     TICK_SIZE (tick_nsec / 1000)

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
 */
irqreturn_t arch_timer_interrupt(int irq, void *dummy)
{
      /* last time the cmos clock got updated */
      static long last_rtc_update=0;

      write_seqlock(&xtime_lock);

      do_timer(1);
#ifndef CONFIG_SMP
      update_process_times(user_mode(get_irq_regs()));
#endif
      if (current->pid)
            profile_tick(CPU_PROFILING);

      /*
       * If we have an externally synchronized Linux clock, then update
       * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
       * called as close as possible to 500 ms before the new second starts.
       */
      if (ntp_synced() &&
          xtime.tv_sec > last_rtc_update + 660 &&
          (xtime.tv_nsec / 1000) >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
          (xtime.tv_nsec  / 1000) <= 500000 + ((unsigned) TICK_SIZE) / 2) {
        if (set_rtc_mmss(xtime.tv_sec) == 0)
          last_rtc_update = xtime.tv_sec;
        else
          last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
      }
#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 */

      write_sequnlock(&xtime_lock);
      return(IRQ_HANDLED);
}

void time_init(void)
{
      unsigned int year, mon, day, hour, min, sec;

      if (mach_gettod)
            mach_gettod(&year, &mon, &day, &hour, &min, &sec);
      else
            year = mon = day = hour = min = sec = 0;

      if ((year += 1900) < 1970)
            year += 100;
      xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
      xtime.tv_nsec = 0;
      wall_to_monotonic.tv_sec = -xtime.tv_sec;

      hw_timer_init();
}

/*
 * This version of gettimeofday has near microsecond resolution.
 */
void do_gettimeofday(struct timeval *tv)
{
      unsigned long flags;
      unsigned long seq;
      unsigned long usec, sec;

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

      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_usec
       * 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 -= (hw_timer_offset() * 1000);

      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);

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