[PATCH] ntp: add ntp_update_frequency

[linux-2.6/linux-2.6-openrd.git] / kernel / time / ntp.c

/*
 * linux/kernel/time/ntp.c
 *
 * NTP state machine interfaces and logic.
 *
 * This code was mainly moved from kernel/timer.c and kernel/time.c
 * Please see those files for relevant copyright info and historical
 * changelogs.
 */

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

#include <asm/div64.h>
#include <asm/timex.h>

/*
 * Timekeeping variables
 */
unsigned long tick_usec = TICK_USEC;            /* USER_HZ period (usec) */
unsigned long tick_nsec;                        /* ACTHZ period (nsec) */
static u64 tick_length, tick_length_base;

/* Don't completely fail for HZ > 500.  */
int tickadj = 500/HZ ? : 1;             /* microsecs */

/*
 * phase-lock loop variables
 */
/* TIME_ERROR prevents overwriting the CMOS clock */
int time_state = TIME_OK;               /* clock synchronization status */
int time_status = STA_UNSYNC;           /* clock status bits            */
long time_offset;                       /* time adjustment (us)         */
long time_constant = 2;                 /* pll time constant            */
long time_tolerance = MAXFREQ;          /* frequency tolerance (ppm)    */
long time_precision = 1;                /* clock precision (us)         */
long time_maxerror = NTP_PHASE_LIMIT;   /* maximum error (us)           */
long time_esterror = NTP_PHASE_LIMIT;   /* estimated error (us)         */
long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
                                        /* frequency offset (scaled ppm)*/
static long time_adj;                   /* tick adjust (scaled 1 / HZ)  */
long time_reftime;                      /* time at last adjustment (s)  */
long time_adjust;
long time_next_adjust;

/**
 * ntp_clear - Clears the NTP state variables
 *
 * Must be called while holding a write on the xtime_lock
 */
void ntp_clear(void)
{
        time_adjust = 0;                /* stop active adjtime() */
        time_status |= STA_UNSYNC;
        time_maxerror = NTP_PHASE_LIMIT;
        time_esterror = NTP_PHASE_LIMIT;

        ntp_update_frequency();

        tick_length = tick_length_base;
}

#define CLOCK_TICK_OVERFLOW     (LATCH * HZ - CLOCK_TICK_RATE)
#define CLOCK_TICK_ADJUST       (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE)

void ntp_update_frequency(void)
{
        tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
        tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;

        do_div(tick_length_base, HZ);

        tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
}

/*
 * this routine handles the overflow of the microsecond field
 *
 * The tricky bits of code to handle the accurate clock support
 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 * They were originally developed for SUN and DEC kernels.
 * All the kudos should go to Dave for this stuff.
 */
void second_overflow(void)
{
        long ltemp;

        /* Bump the maxerror field */
        time_maxerror += time_tolerance >> SHIFT_USEC;
        if (time_maxerror > NTP_PHASE_LIMIT) {
                time_maxerror = NTP_PHASE_LIMIT;
                time_status |= STA_UNSYNC;
        }

        /*
         * Leap second processing. If in leap-insert state at the end of the
         * day, the system clock is set back one second; if in leap-delete
         * state, the system clock is set ahead one second. The microtime()
         * routine or external clock driver will insure that reported time is
         * always monotonic. The ugly divides should be replaced.
         */
        switch (time_state) {
        case TIME_OK:
                if (time_status & STA_INS)
                        time_state = TIME_INS;
                else if (time_status & STA_DEL)
                        time_state = TIME_DEL;
                break;
        case TIME_INS:
                if (xtime.tv_sec % 86400 == 0) {
                        xtime.tv_sec--;
                        wall_to_monotonic.tv_sec++;
                        /*
                         * The timer interpolator will make time change
                         * gradually instead of an immediate jump by one second
                         */
                        time_interpolator_update(-NSEC_PER_SEC);
                        time_state = TIME_OOP;
                        clock_was_set();
                        printk(KERN_NOTICE "Clock: inserting leap second "
                                        "23:59:60 UTC\n");
                }
                break;
        case TIME_DEL:
                if ((xtime.tv_sec + 1) % 86400 == 0) {
                        xtime.tv_sec++;
                        wall_to_monotonic.tv_sec--;
                        /*
                         * Use of time interpolator for a gradual change of
                         * time
                         */
                        time_interpolator_update(NSEC_PER_SEC);
                        time_state = TIME_WAIT;
                        clock_was_set();
                        printk(KERN_NOTICE "Clock: deleting leap second "
                                        "23:59:59 UTC\n");
                }
                break;
        case TIME_OOP:
                time_state = TIME_WAIT;
                break;
        case TIME_WAIT:
                if (!(time_status & (STA_INS | STA_DEL)))
                time_state = TIME_OK;
        }

        /*
         * Compute the phase adjustment for the next second. In PLL mode, the
         * offset is reduced by a fixed factor times the time constant. In FLL
         * mode the offset is used directly. In either mode, the maximum phase
         * adjustment for each second is clamped so as to spread the adjustment
         * over not more than the number of seconds between updates.
         */
        ltemp = time_offset;
        if (!(time_status & STA_FLL))
                ltemp = shift_right(ltemp, SHIFT_KG + time_constant);
        ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
        ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
        time_offset -= ltemp;
        time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);

        /*
         * Compute the frequency estimate and additional phase adjustment due
         * to frequency error for the next second.
         */
        ltemp = time_freq;
        time_adj += shift_right(ltemp,(SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));

#if HZ == 100
        /*
         * Compensate for (HZ==100) != (1 << SHIFT_HZ).  Add 25% and 3.125% to
         * get 128.125; => only 0.125% error (p. 14)
         */
        time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5);
#endif
#if HZ == 250
        /*
         * Compensate for (HZ==250) != (1 << SHIFT_HZ).  Add 1.5625% and
         * 0.78125% to get 255.85938; => only 0.05% error (p. 14)
         */
        time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
#endif
#if HZ == 1000
        /*
         * Compensate for (HZ==1000) != (1 << SHIFT_HZ).  Add 1.5625% and
         * 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
         */
        time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
#endif
        tick_length = tick_length_base;
}

/*
 * Returns how many microseconds we need to add to xtime this tick
 * in doing an adjustment requested with adjtime.
 */
static long adjtime_adjustment(void)
{
        long time_adjust_step;

        time_adjust_step = time_adjust;
        if (time_adjust_step) {
                /*
                 * We are doing an adjtime thing.  Prepare time_adjust_step to
                 * be within bounds.  Note that a positive time_adjust means we
                 * want the clock to run faster.
                 *
                 * Limit the amount of the step to be in the range
                 * -tickadj .. +tickadj
                 */
                time_adjust_step = min(time_adjust_step, (long)tickadj);
                time_adjust_step = max(time_adjust_step, (long)-tickadj);
        }
        return time_adjust_step;
}

/* in the NTP reference this is called "hardclock()" */
void update_ntp_one_tick(void)
{
        long time_adjust_step;

        time_adjust_step = adjtime_adjustment();
        if (time_adjust_step)
                /* Reduce by this step the amount of time left  */
                time_adjust -= time_adjust_step;

        /* Changes by adjtime() do not take effect till next tick. */
        if (time_next_adjust != 0) {
                time_adjust = time_next_adjust;
                time_next_adjust = 0;
        }
}

/*
 * Return how long ticks are at the moment, that is, how much time
 * update_wall_time_one_tick will add to xtime next time we call it
 * (assuming no calls to do_adjtimex in the meantime).
 * The return value is in fixed-point nanoseconds shifted by the
 * specified number of bits to the right of the binary point.
 * This function has no side-effects.
 */
u64 current_tick_length(void)
{
        u64 ret;

        /* calculate the finest interval NTP will allow.
         *    ie: nanosecond value shifted by (SHIFT_SCALE - 10)
         */
        ret = tick_length;
        ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
        ret += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));

        return ret;
}


void __attribute__ ((weak)) notify_arch_cmos_timer(void)
{
        return;
}

/* adjtimex mainly allows reading (and writing, if superuser) of
 * kernel time-keeping variables. used by xntpd.
 */
int do_adjtimex(struct timex *txc)
{
        long ltemp, mtemp, save_adjust;
        int result;

        /* In order to modify anything, you gotta be super-user! */
        if (txc->modes && !capable(CAP_SYS_TIME))
                return -EPERM;

        /* Now we validate the data before disabling interrupts */

        if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
          /* singleshot must not be used with any other mode bits */
                if (txc->modes != ADJ_OFFSET_SINGLESHOT)
                        return -EINVAL;

        if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
          /* adjustment Offset limited to +- .512 seconds */
                if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
                        return -EINVAL;

        /* if the quartz is off by more than 10% something is VERY wrong ! */
        if (txc->modes & ADJ_TICK)
                if (txc->tick <  900000/USER_HZ ||
                    txc->tick > 1100000/USER_HZ)
                        return -EINVAL;

        write_seqlock_irq(&xtime_lock);
        result = time_state;    /* mostly `TIME_OK' */

        /* Save for later - semantics of adjtime is to return old value */
        save_adjust = time_next_adjust ? time_next_adjust : time_adjust;

#if 0   /* STA_CLOCKERR is never set yet */
        time_status &= ~STA_CLOCKERR;           /* reset STA_CLOCKERR */
#endif
        /* If there are input parameters, then process them */
        if (txc->modes)
        {
            if (txc->modes & ADJ_STATUS)        /* only set allowed bits */
                time_status =  (txc->status & ~STA_RONLY) |
                              (time_status & STA_RONLY);

            if (txc->modes & ADJ_FREQUENCY) {   /* p. 22 */
                if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
                    result = -EINVAL;
                    goto leave;
                }
                time_freq = txc->freq;
            }

            if (txc->modes & ADJ_MAXERROR) {
                if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
                    result = -EINVAL;
                    goto leave;
                }
                time_maxerror = txc->maxerror;
            }

            if (txc->modes & ADJ_ESTERROR) {
                if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
                    result = -EINVAL;
                    goto leave;
                }
                time_esterror = txc->esterror;
            }

            if (txc->modes & ADJ_TIMECONST) {   /* p. 24 */
                if (txc->constant < 0) {        /* NTP v4 uses values > 6 */
                    result = -EINVAL;
                    goto leave;
                }
                time_constant = txc->constant;
            }

            if (txc->modes & ADJ_OFFSET) {      /* values checked earlier */
                if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
                    /* adjtime() is independent from ntp_adjtime() */
                    if ((time_next_adjust = txc->offset) == 0)
                         time_adjust = 0;
                }
                else if (time_status & STA_PLL) {
                    ltemp = txc->offset;

                    /*
                     * Scale the phase adjustment and
                     * clamp to the operating range.
                     */
                    if (ltemp > MAXPHASE)
                        time_offset = MAXPHASE << SHIFT_UPDATE;
                    else if (ltemp < -MAXPHASE)
                        time_offset = -(MAXPHASE << SHIFT_UPDATE);
                    else
                        time_offset = ltemp << SHIFT_UPDATE;

                    /*
                     * Select whether the frequency is to be controlled
                     * and in which mode (PLL or FLL). Clamp to the operating
                     * range. Ugly multiply/divide should be replaced someday.
                     */

                    if (time_status & STA_FREQHOLD || time_reftime == 0)
                        time_reftime = xtime.tv_sec;
                    mtemp = xtime.tv_sec - time_reftime;
                    time_reftime = xtime.tv_sec;
                    if (time_status & STA_FLL) {
                        if (mtemp >= MINSEC) {
                            ltemp = (time_offset / mtemp) << (SHIFT_USEC -
                                                              SHIFT_UPDATE);
                            time_freq += shift_right(ltemp, SHIFT_KH);
                        } else /* calibration interval too short (p. 12) */
                                result = TIME_ERROR;
                    } else {    /* PLL mode */
                        if (mtemp < MAXSEC) {
                            ltemp *= mtemp;
                            time_freq += shift_right(ltemp,(time_constant +
                                                       time_constant +
                                                       SHIFT_KF - SHIFT_USEC));
                        } else /* calibration interval too long (p. 12) */
                                result = TIME_ERROR;
                    }
                    time_freq = min(time_freq, time_tolerance);
                    time_freq = max(time_freq, -time_tolerance);
                } /* STA_PLL */
            } /* txc->modes & ADJ_OFFSET */
            if (txc->modes & ADJ_TICK)
                tick_usec = txc->tick;

            if (txc->modes & ADJ_TICK)
                    ntp_update_frequency();
        } /* txc->modes */
leave:  if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
                result = TIME_ERROR;

        if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
            txc->offset    = save_adjust;
        else {
            txc->offset = shift_right(time_offset, SHIFT_UPDATE);
        }
        txc->freq          = time_freq;
        txc->maxerror      = time_maxerror;
        txc->esterror      = time_esterror;
        txc->status        = time_status;
        txc->constant      = time_constant;
        txc->precision     = time_precision;
        txc->tolerance     = time_tolerance;
        txc->tick          = tick_usec;

        /* PPS is not implemented, so these are zero */
        txc->ppsfreq       = 0;
        txc->jitter        = 0;
        txc->shift         = 0;
        txc->stabil        = 0;
        txc->jitcnt        = 0;
        txc->calcnt        = 0;
        txc->errcnt        = 0;
        txc->stbcnt        = 0;
        write_sequnlock_irq(&xtime_lock);
        do_gettimeofday(&txc->time);
        notify_arch_cmos_timer();
        return(result);
}