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/*

 * 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/timer.h>

#include <linux/timex.h>

#include <linux/jiffies.h>

#include <linux/hrtimer.h>

#include <linux/capability.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;

#define MAX_TICKADJ             500             /* microsecs */

#define MAX_TICKADJ_SCALED      (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \

                                  TICK_LENGTH_SHIFT) / NTP_INTERVAL_FREQ)

/*

 * phase-lock loop variables

 */

/* TIME_ERROR prevents overwriting the CMOS clock */

static int time_state = TIME_OK;        /* clock synchronization status */

int time_status = STA_UNSYNC;           /* clock status bits            */

static s64 time_offset;         /* time adjustment (ns)         */

static long time_constant = 2;          /* pll time constant            */

long time_maxerror = NTP_PHASE_LIMIT;   /* maximum error (us)           */

long time_esterror = NTP_PHASE_LIMIT;   /* estimated error (us)         */

long time_freq;                         /* frequency offset (scaled ppm)*/

static long time_reftime;               /* time at last adjustment (s)  */

long time_adjust;

#define CLOCK_TICK_OVERFLOW     (LATCH * HZ - CLOCK_TICK_RATE)

#define CLOCK_TICK_ADJUST       (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \

                                        (s64)CLOCK_TICK_RATE)

static void ntp_update_frequency(void)

{

        u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)

                                << TICK_LENGTH_SHIFT;

        second_length += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;

        second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);

        tick_length_base = second_length;

        do_div(second_length, HZ);

        tick_nsec = second_length >> TICK_LENGTH_SHIFT;

        do_div(tick_length_base, NTP_INTERVAL_FREQ);

}

/**

 * 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;

        time_offset = 0;

}

/*

 * 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 time_adj;

        /* Bump the maxerror field */

        time_maxerror += MAXFREQ >> 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++;

                        time_state = TIME_OOP;

                        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--;

                        time_state = TIME_WAIT;

                        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. The offset is

         * reduced by a fixed factor times the time constant.

         */

        tick_length = tick_length_base;

        time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);

        time_offset -= time_adj;

        tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);

        if (unlikely(time_adjust)) {

                if (time_adjust > MAX_TICKADJ) {

                        time_adjust -= MAX_TICKADJ;

                        tick_length += MAX_TICKADJ_SCALED;

                } else if (time_adjust < -MAX_TICKADJ) {

                        time_adjust += MAX_TICKADJ;

                        tick_length -= MAX_TICKADJ_SCALED;

                } else {

                        tick_length += (s64)(time_adjust * NSEC_PER_USEC /

                                        NTP_INTERVAL_FREQ) << TICK_LENGTH_SHIFT;

                        time_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)

{

        return tick_length;

}

#ifdef CONFIG_GENERIC_CMOS_UPDATE

/* Disable the cmos update - used by virtualization and embedded */

int no_sync_cmos_clock  __read_mostly;

static void sync_cmos_clock(unsigned long dummy);

static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);

static void sync_cmos_clock(unsigned long dummy)

{

        struct timespec now, next;

        int fail = 1;

        /*

         * 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.

         * This code is run on a timer.  If the clock is set, that timer

         * may not expire at the correct time.  Thus, we adjust...

         */

        if (!ntp_synced())

                /*

                 * Not synced, exit, do not restart a timer (if one is

                 * running, let it run out).

                 */

                return;

        getnstimeofday(&now);

        if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)

                fail = update_persistent_clock(now);

        next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec;

        if (next.tv_nsec <= 0)

                next.tv_nsec += NSEC_PER_SEC;

        if (!fail)

                next.tv_sec = 659;

        else

                next.tv_sec = 0;

        if (next.tv_nsec >= NSEC_PER_SEC) {

                next.tv_sec++;

                next.tv_nsec -= NSEC_PER_SEC;

        }

        mod_timer(&sync_cmos_timer, jiffies + timespec_to_jiffies(&next));

}

static void notify_cmos_timer(void)

{

        if (!no_sync_cmos_clock)

                mod_timer(&sync_cmos_timer, jiffies + 1);

}

#else

static inline void notify_cmos_timer(void) { }

#endif

/* adjtimex mainly allows reading (and writing, if superuser) of

 * kernel time-keeping variables. used by xntpd.

 */

int do_adjtimex(struct timex *txc)

{

        long mtemp, save_adjust, rem;

        s64 freq_adj, temp64;

        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 &&

                                        txc->modes != ADJ_OFFSET_SS_READ)

                        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_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 = ((s64)txc->freq * NSEC_PER_USEC)

                                >> (SHIFT_USEC - SHIFT_NSEC);

            }

            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 = min(txc->constant + 4, (long)MAXTC);

            }

            if (txc->modes & ADJ_OFFSET) {      /* values checked earlier */

                if (txc->modes == ADJ_OFFSET_SINGLESHOT) {

                    /* adjtime() is independent from ntp_adjtime() */

                    time_adjust = txc->offset;

                }

                else if (time_status & STA_PLL) {

                    time_offset = txc->offset * NSEC_PER_USEC;

                    /*

                     * Scale the phase adjustment and

                     * clamp to the operating range.

                     */

                    time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC);

                    time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC);

                    /*

                     * 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;

                    freq_adj = time_offset * mtemp;

                    freq_adj = shift_right(freq_adj, time_constant * 2 +

                                           (SHIFT_PLL + 2) * 2 - SHIFT_NSEC);

                    if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {

                        temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL);

                        if (time_offset < 0) {

                            temp64 = -temp64;

                            do_div(temp64, mtemp);

                            freq_adj -= temp64;

                        } else {

                            do_div(temp64, mtemp);

                            freq_adj += temp64;

                        }

                    }

                    freq_adj += time_freq;

                    freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);

                    time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);

                    time_offset = div_long_long_rem_signed(time_offset,

                                                           NTP_INTERVAL_FREQ,

                                                           &rem);

                    time_offset <<= SHIFT_UPDATE;

                } /* STA_PLL */

            } /* txc->modes & ADJ_OFFSET */

            if (txc->modes & ADJ_TICK)

                tick_usec = txc->tick;

            if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))

                    ntp_update_frequency();

        } /* txc->modes */

leave:  if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)

                result = TIME_ERROR;

        if ((txc->modes == ADJ_OFFSET_SINGLESHOT) ||

                        (txc->modes == ADJ_OFFSET_SS_READ))

                txc->offset = save_adjust;

        else

                txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *

                                NTP_INTERVAL_FREQ / 1000;

        txc->freq          = (time_freq / NSEC_PER_USEC) <<

                                (SHIFT_USEC - SHIFT_NSEC);

        txc->maxerror      = time_maxerror;

        txc->esterror      = time_esterror;

        txc->status        = time_status;

        txc->constant      = time_constant;

        txc->precision     = 1;

        txc->tolerance     = MAXFREQ;

        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_cmos_timer();

        return(result);

}