drm/modes: Fix drm_mode_vrefres() docs

[drm/drm-misc.git] / kernel / time / ntp.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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/capability.h>
#include <linux/clocksource.h>
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
#include <linux/jiffies.h>
#include <linux/math64.h>
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/audit.h>

#include "ntp_internal.h"
#include "timekeeping_internal.h"

/**
 * struct ntp_data - Structure holding all NTP related state
 * @tick_usec:          USER_HZ period in microseconds
 * @tick_length:        Adjusted tick length
 * @tick_length_base:   Base value for @tick_length
 * @time_state:         State of the clock synchronization
 * @time_status:        Clock status bits
 * @time_offset:        Time adjustment in nanoseconds
 * @time_constant:      PLL time constant
 * @time_maxerror:      Maximum error in microseconds holding the NTP sync distance
 *                      (NTP dispersion + delay / 2)
 * @time_esterror:      Estimated error in microseconds holding NTP dispersion
 * @time_freq:          Frequency offset scaled nsecs/secs
 * @time_reftime:       Time at last adjustment in seconds
 * @time_adjust:        Adjustment value
 * @ntp_tick_adj:       Constant boot-param configurable NTP tick adjustment (upscaled)
 * @ntp_next_leap_sec:  Second value of the next pending leapsecond, or TIME64_MAX if no leap
 *
 * @pps_valid:          PPS signal watchdog counter
 * @pps_tf:             PPS phase median filter
 * @pps_jitter:         PPS current jitter in nanoseconds
 * @pps_fbase:          PPS beginning of the last freq interval
 * @pps_shift:          PPS current interval duration in seconds (shift value)
 * @pps_intcnt:         PPS interval counter
 * @pps_freq:           PPS frequency offset in scaled ns/s
 * @pps_stabil:         PPS current stability in scaled ns/s
 * @pps_calcnt:         PPS monitor: calibration intervals
 * @pps_jitcnt:         PPS monitor: jitter limit exceeded
 * @pps_stbcnt:         PPS monitor: stability limit exceeded
 * @pps_errcnt:         PPS monitor: calibration errors
 *
 * Protected by the timekeeping locks.
 */
struct ntp_data {
        unsigned long           tick_usec;
        u64                     tick_length;
        u64                     tick_length_base;
        int                     time_state;
        int                     time_status;
        s64                     time_offset;
        long                    time_constant;
        long                    time_maxerror;
        long                    time_esterror;
        s64                     time_freq;
        time64_t                time_reftime;
        long                    time_adjust;
        s64                     ntp_tick_adj;
        time64_t                ntp_next_leap_sec;
#ifdef CONFIG_NTP_PPS
        int                     pps_valid;
        long                    pps_tf[3];
        long                    pps_jitter;
        struct timespec64       pps_fbase;
        int                     pps_shift;
        int                     pps_intcnt;
        s64                     pps_freq;
        long                    pps_stabil;
        long                    pps_calcnt;
        long                    pps_jitcnt;
        long                    pps_stbcnt;
        long                    pps_errcnt;
#endif
};

static struct ntp_data tk_ntp_data = {
        .tick_usec              = USER_TICK_USEC,
        .time_state             = TIME_OK,
        .time_status            = STA_UNSYNC,
        .time_constant          = 2,
        .time_maxerror          = NTP_PHASE_LIMIT,
        .time_esterror          = NTP_PHASE_LIMIT,
        .ntp_next_leap_sec      = TIME64_MAX,
};

#define SECS_PER_DAY            86400
#define MAX_TICKADJ             500LL           /* usecs */
#define MAX_TICKADJ_SCALED \
        (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
#define MAX_TAI_OFFSET          100000

#ifdef CONFIG_NTP_PPS

/*
 * The following variables are used when a pulse-per-second (PPS) signal
 * is available. They establish the engineering parameters of the clock
 * discipline loop when controlled by the PPS signal.
 */
#define PPS_VALID       10      /* PPS signal watchdog max (s) */
#define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
#define PPS_INTMIN      2       /* min freq interval (s) (shift) */
#define PPS_INTMAX      8       /* max freq interval (s) (shift) */
#define PPS_INTCOUNT    4       /* number of consecutive good intervals to
                                   increase pps_shift or consecutive bad
                                   intervals to decrease it */
#define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */

/*
 * PPS kernel consumer compensates the whole phase error immediately.
 * Otherwise, reduce the offset by a fixed factor times the time constant.
 */
static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
{
        if (ntpdata->time_status & STA_PPSTIME && ntpdata->time_status & STA_PPSSIGNAL)
                return offset;
        else
                return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
}

static inline void pps_reset_freq_interval(struct ntp_data *ntpdata)
{
        /* The PPS calibration interval may end surprisingly early */
        ntpdata->pps_shift = PPS_INTMIN;
        ntpdata->pps_intcnt = 0;
}

/**
 * pps_clear - Clears the PPS state variables
 * @ntpdata:    Pointer to ntp data
 */
static inline void pps_clear(struct ntp_data *ntpdata)
{
        pps_reset_freq_interval(ntpdata);
        ntpdata->pps_tf[0] = 0;
        ntpdata->pps_tf[1] = 0;
        ntpdata->pps_tf[2] = 0;
        ntpdata->pps_fbase.tv_sec = ntpdata->pps_fbase.tv_nsec = 0;
        ntpdata->pps_freq = 0;
}

/*
 * Decrease pps_valid to indicate that another second has passed since the
 * last PPS signal. When it reaches 0, indicate that PPS signal is missing.
 */
static inline void pps_dec_valid(struct ntp_data *ntpdata)
{
        if (ntpdata->pps_valid > 0) {
                ntpdata->pps_valid--;
        } else {
                ntpdata->time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
                                          STA_PPSWANDER | STA_PPSERROR);
                pps_clear(ntpdata);
        }
}

static inline void pps_set_freq(struct ntp_data *ntpdata)
{
        ntpdata->pps_freq = ntpdata->time_freq;
}

static inline bool is_error_status(int status)
{
        return (status & (STA_UNSYNC|STA_CLOCKERR))
                /*
                 * PPS signal lost when either PPS time or PPS frequency
                 * synchronization requested
                 */
                || ((status & (STA_PPSFREQ|STA_PPSTIME))
                        && !(status & STA_PPSSIGNAL))
                /*
                 * PPS jitter exceeded when PPS time synchronization
                 * requested
                 */
                || ((status & (STA_PPSTIME|STA_PPSJITTER))
                        == (STA_PPSTIME|STA_PPSJITTER))
                /*
                 * PPS wander exceeded or calibration error when PPS
                 * frequency synchronization requested
                 */
                || ((status & STA_PPSFREQ)
                        && (status & (STA_PPSWANDER|STA_PPSERROR)));
}

static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
{
        txc->ppsfreq       = shift_right((ntpdata->pps_freq >> PPM_SCALE_INV_SHIFT) *
                                         PPM_SCALE_INV, NTP_SCALE_SHIFT);
        txc->jitter        = ntpdata->pps_jitter;
        if (!(ntpdata->time_status & STA_NANO))
                txc->jitter = ntpdata->pps_jitter / NSEC_PER_USEC;
        txc->shift         = ntpdata->pps_shift;
        txc->stabil        = ntpdata->pps_stabil;
        txc->jitcnt        = ntpdata->pps_jitcnt;
        txc->calcnt        = ntpdata->pps_calcnt;
        txc->errcnt        = ntpdata->pps_errcnt;
        txc->stbcnt        = ntpdata->pps_stbcnt;
}

#else /* !CONFIG_NTP_PPS */

static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
{
        return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
}

static inline void pps_reset_freq_interval(struct ntp_data *ntpdata) {}
static inline void pps_clear(struct ntp_data *ntpdata) {}
static inline void pps_dec_valid(struct ntp_data *ntpdata) {}
static inline void pps_set_freq(struct ntp_data *ntpdata) {}

static inline bool is_error_status(int status)
{
        return status & (STA_UNSYNC|STA_CLOCKERR);
}

static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
{
        /* 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;
}

#endif /* CONFIG_NTP_PPS */

/*
 * Update tick_length and tick_length_base, based on tick_usec, ntp_tick_adj and
 * time_freq:
 */
static void ntp_update_frequency(struct ntp_data *ntpdata)
{
        u64 second_length, new_base, tick_usec = (u64)ntpdata->tick_usec;

        second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT;

        second_length           += ntpdata->ntp_tick_adj;
        second_length           += ntpdata->time_freq;

        new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);

        /*
         * Don't wait for the next second_overflow, apply the change to the
         * tick length immediately:
         */
        ntpdata->tick_length            += new_base - ntpdata->tick_length_base;
        ntpdata->tick_length_base        = new_base;
}

static inline s64 ntp_update_offset_fll(struct ntp_data *ntpdata, s64 offset64, long secs)
{
        ntpdata->time_status &= ~STA_MODE;

        if (secs < MINSEC)
                return 0;

        if (!(ntpdata->time_status & STA_FLL) && (secs <= MAXSEC))
                return 0;

        ntpdata->time_status |= STA_MODE;

        return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
}

static void ntp_update_offset(struct ntp_data *ntpdata, long offset)
{
        s64 freq_adj, offset64;
        long secs, real_secs;

        if (!(ntpdata->time_status & STA_PLL))
                return;

        if (!(ntpdata->time_status & STA_NANO)) {
                /* Make sure the multiplication below won't overflow */
                offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
                offset *= NSEC_PER_USEC;
        }

        /* Scale the phase adjustment and clamp to the operating range. */
        offset = clamp(offset, -MAXPHASE, MAXPHASE);

        /*
         * Select how the frequency is to be controlled
         * and in which mode (PLL or FLL).
         */
        real_secs = __ktime_get_real_seconds();
        secs = (long)(real_secs - ntpdata->time_reftime);
        if (unlikely(ntpdata->time_status & STA_FREQHOLD))
                secs = 0;

        ntpdata->time_reftime = real_secs;

        offset64    = offset;
        freq_adj    = ntp_update_offset_fll(ntpdata, offset64, secs);

        /*
         * Clamp update interval to reduce PLL gain with low
         * sampling rate (e.g. intermittent network connection)
         * to avoid instability.
         */
        if (unlikely(secs > 1 << (SHIFT_PLL + 1 + ntpdata->time_constant)))
                secs = 1 << (SHIFT_PLL + 1 + ntpdata->time_constant);

        freq_adj    += (offset64 * secs) <<
                        (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + ntpdata->time_constant));

        freq_adj    = min(freq_adj + ntpdata->time_freq, MAXFREQ_SCALED);

        ntpdata->time_freq   = max(freq_adj, -MAXFREQ_SCALED);

        ntpdata->time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
}

static void __ntp_clear(struct ntp_data *ntpdata)
{
        /* Stop active adjtime() */
        ntpdata->time_adjust    = 0;
        ntpdata->time_status    |= STA_UNSYNC;
        ntpdata->time_maxerror  = NTP_PHASE_LIMIT;
        ntpdata->time_esterror  = NTP_PHASE_LIMIT;

        ntp_update_frequency(ntpdata);

        ntpdata->tick_length    = ntpdata->tick_length_base;
        ntpdata->time_offset    = 0;

        ntpdata->ntp_next_leap_sec = TIME64_MAX;
        /* Clear PPS state variables */
        pps_clear(ntpdata);
}

/**
 * ntp_clear - Clears the NTP state variables
 */
void ntp_clear(void)
{
        __ntp_clear(&tk_ntp_data);
}


u64 ntp_tick_length(void)
{
        return tk_ntp_data.tick_length;
}

/**
 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
 *
 * Provides the time of the next leapsecond against CLOCK_REALTIME in
 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
 */
ktime_t ntp_get_next_leap(void)
{
        struct ntp_data *ntpdata = &tk_ntp_data;
        ktime_t ret;

        if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS))
                return ktime_set(ntpdata->ntp_next_leap_sec, 0);
        ret = KTIME_MAX;
        return ret;
}

/*
 * 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.
 *
 * Also handles leap second processing, and returns leap offset
 */
int second_overflow(time64_t secs)
{
        struct ntp_data *ntpdata = &tk_ntp_data;
        s64 delta;
        int leap = 0;
        s32 rem;

        /*
         * 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.
         */
        switch (ntpdata->time_state) {
        case TIME_OK:
                if (ntpdata->time_status & STA_INS) {
                        ntpdata->time_state = TIME_INS;
                        div_s64_rem(secs, SECS_PER_DAY, &rem);
                        ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
                } else if (ntpdata->time_status & STA_DEL) {
                        ntpdata->time_state = TIME_DEL;
                        div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
                        ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
                }
                break;
        case TIME_INS:
                if (!(ntpdata->time_status & STA_INS)) {
                        ntpdata->ntp_next_leap_sec = TIME64_MAX;
                        ntpdata->time_state = TIME_OK;
                } else if (secs == ntpdata->ntp_next_leap_sec) {
                        leap = -1;
                        ntpdata->time_state = TIME_OOP;
                        pr_notice("Clock: inserting leap second 23:59:60 UTC\n");
                }
                break;
        case TIME_DEL:
                if (!(ntpdata->time_status & STA_DEL)) {
                        ntpdata->ntp_next_leap_sec = TIME64_MAX;
                        ntpdata->time_state = TIME_OK;
                } else if (secs == ntpdata->ntp_next_leap_sec) {
                        leap = 1;
                        ntpdata->ntp_next_leap_sec = TIME64_MAX;
                        ntpdata->time_state = TIME_WAIT;
                        pr_notice("Clock: deleting leap second 23:59:59 UTC\n");
                }
                break;
        case TIME_OOP:
                ntpdata->ntp_next_leap_sec = TIME64_MAX;
                ntpdata->time_state = TIME_WAIT;
                break;
        case TIME_WAIT:
                if (!(ntpdata->time_status & (STA_INS | STA_DEL)))
                        ntpdata->time_state = TIME_OK;
                break;
        }

        /* Bump the maxerror field */
        ntpdata->time_maxerror += MAXFREQ / NSEC_PER_USEC;
        if (ntpdata->time_maxerror > NTP_PHASE_LIMIT) {
                ntpdata->time_maxerror = NTP_PHASE_LIMIT;
                ntpdata->time_status |= STA_UNSYNC;
        }

        /* Compute the phase adjustment for the next second */
        ntpdata->tick_length     = ntpdata->tick_length_base;

        delta                    = ntp_offset_chunk(ntpdata, ntpdata->time_offset);
        ntpdata->time_offset    -= delta;
        ntpdata->tick_length    += delta;

        /* Check PPS signal */
        pps_dec_valid(ntpdata);

        if (!ntpdata->time_adjust)
                goto out;

        if (ntpdata->time_adjust > MAX_TICKADJ) {
                ntpdata->time_adjust -= MAX_TICKADJ;
                ntpdata->tick_length += MAX_TICKADJ_SCALED;
                goto out;
        }

        if (ntpdata->time_adjust < -MAX_TICKADJ) {
                ntpdata->time_adjust += MAX_TICKADJ;
                ntpdata->tick_length -= MAX_TICKADJ_SCALED;
                goto out;
        }

        ntpdata->tick_length += (s64)(ntpdata->time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
                                << NTP_SCALE_SHIFT;
        ntpdata->time_adjust = 0;

out:
        return leap;
}

#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
static void sync_hw_clock(struct work_struct *work);
static DECLARE_WORK(sync_work, sync_hw_clock);
static struct hrtimer sync_hrtimer;
#define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)

static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
{
        queue_work(system_freezable_power_efficient_wq, &sync_work);

        return HRTIMER_NORESTART;
}

static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
{
        ktime_t exp = ktime_set(ktime_get_real_seconds(), 0);

        if (retry)
                exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
        else
                exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);

        hrtimer_start(&sync_hrtimer, exp, HRTIMER_MODE_ABS);
}

/*
 * Check whether @now is correct versus the required time to update the RTC
 * and calculate the value which needs to be written to the RTC so that the
 * next seconds increment of the RTC after the write is aligned with the next
 * seconds increment of clock REALTIME.
 *
 * tsched     t1 write(t2.tv_sec - 1sec))       t2 RTC increments seconds
 *
 * t2.tv_nsec == 0
 * tsched = t2 - set_offset_nsec
 * newval = t2 - NSEC_PER_SEC
 *
 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
 *
 * As the execution of this code is not guaranteed to happen exactly at
 * tsched this allows it to happen within a fuzzy region:
 *
 *      abs(now - tsched) < FUZZ
 *
 * If @now is not inside the allowed window the function returns false.
 */
static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
                                  struct timespec64 *to_set,
                                  const struct timespec64 *now)
{
        /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
        const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
        struct timespec64 delay = {.tv_sec = -1,
                                   .tv_nsec = set_offset_nsec};

        *to_set = timespec64_add(*now, delay);

        if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
                to_set->tv_nsec = 0;
                return true;
        }

        if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
                to_set->tv_sec++;
                to_set->tv_nsec = 0;
                return true;
        }
        return false;
}

#ifdef CONFIG_GENERIC_CMOS_UPDATE
int __weak update_persistent_clock64(struct timespec64 now64)
{
        return -ENODEV;
}
#else
static inline int update_persistent_clock64(struct timespec64 now64)
{
        return -ENODEV;
}
#endif

#ifdef CONFIG_RTC_SYSTOHC
/* Save NTP synchronized time to the RTC */
static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
{
        struct rtc_device *rtc;
        struct rtc_time tm;
        int err = -ENODEV;

        rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
        if (!rtc)
                return -ENODEV;

        if (!rtc->ops || !rtc->ops->set_time)
                goto out_close;

        /* First call might not have the correct offset */
        if (*offset_nsec == rtc->set_offset_nsec) {
                rtc_time64_to_tm(to_set->tv_sec, &tm);
                err = rtc_set_time(rtc, &tm);
        } else {
                /* Store the update offset and let the caller try again */
                *offset_nsec = rtc->set_offset_nsec;
                err = -EAGAIN;
        }
out_close:
        rtc_class_close(rtc);
        return err;
}
#else
static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
{
        return -ENODEV;
}
#endif

/**
 * ntp_synced - Tells whether the NTP status is not UNSYNC
 * Returns:     true if not UNSYNC, false otherwise
 */
static inline bool ntp_synced(void)
{
        return !(tk_ntp_data.time_status & STA_UNSYNC);
}

/*
 * If we have an externally synchronized Linux clock, then update RTC clock
 * accordingly every ~11 minutes. Generally RTCs can only store second
 * precision, but many RTCs will adjust the phase of their second tick to
 * match the moment of update. This infrastructure arranges to call to the RTC
 * set at the correct moment to phase synchronize the RTC second tick over
 * with the kernel clock.
 */
static void sync_hw_clock(struct work_struct *work)
{
        /*
         * The default synchronization offset is 500ms for the deprecated
         * update_persistent_clock64() under the assumption that it uses
         * the infamous CMOS clock (MC146818).
         */
        static unsigned long offset_nsec = NSEC_PER_SEC / 2;
        struct timespec64 now, to_set;
        int res = -EAGAIN;

        /*
         * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
         * managed to schedule the work between the timer firing and the
         * work being able to rearm the timer. Wait for the timer to expire.
         */
        if (!ntp_synced() || hrtimer_is_queued(&sync_hrtimer))
                return;

        ktime_get_real_ts64(&now);
        /* If @now is not in the allowed window, try again */
        if (!rtc_tv_nsec_ok(offset_nsec, &to_set, &now))
                goto rearm;

        /* Take timezone adjusted RTCs into account */
        if (persistent_clock_is_local)
                to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);

        /* Try the legacy RTC first. */
        res = update_persistent_clock64(to_set);
        if (res != -ENODEV)
                goto rearm;

        /* Try the RTC class */
        res = update_rtc(&to_set, &offset_nsec);
        if (res == -ENODEV)
                return;
rearm:
        sched_sync_hw_clock(offset_nsec, res != 0);
}

void ntp_notify_cmos_timer(bool offset_set)
{
        /*
         * If the time jumped (using ADJ_SETOFFSET) cancels sync timer,
         * which may have been running if the time was synchronized
         * prior to the ADJ_SETOFFSET call.
         */
        if (offset_set)
                hrtimer_cancel(&sync_hrtimer);

        /*
         * When the work is currently executed but has not yet the timer
         * rearmed this queues the work immediately again. No big issue,
         * just a pointless work scheduled.
         */
        if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
                queue_work(system_freezable_power_efficient_wq, &sync_work);
}

static void __init ntp_init_cmos_sync(void)
{
        hrtimer_init(&sync_hrtimer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
        sync_hrtimer.function = sync_timer_callback;
}
#else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
static inline void __init ntp_init_cmos_sync(void) { }
#endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */

/*
 * Propagate a new txc->status value into the NTP state:
 */
static inline void process_adj_status(struct ntp_data *ntpdata, const struct __kernel_timex *txc)
{
        if ((ntpdata->time_status & STA_PLL) && !(txc->status & STA_PLL)) {
                ntpdata->time_state = TIME_OK;
                ntpdata->time_status = STA_UNSYNC;
                ntpdata->ntp_next_leap_sec = TIME64_MAX;
                /* Restart PPS frequency calibration */
                pps_reset_freq_interval(ntpdata);
        }

        /*
         * If we turn on PLL adjustments then reset the
         * reference time to current time.
         */
        if (!(ntpdata->time_status & STA_PLL) && (txc->status & STA_PLL))
                ntpdata->time_reftime = __ktime_get_real_seconds();

        /* only set allowed bits */
        ntpdata->time_status &= STA_RONLY;
        ntpdata->time_status |= txc->status & ~STA_RONLY;
}

static inline void process_adjtimex_modes(struct ntp_data *ntpdata, const struct __kernel_timex *txc,
                                          s32 *time_tai)
{
        if (txc->modes & ADJ_STATUS)
                process_adj_status(ntpdata, txc);

        if (txc->modes & ADJ_NANO)
                ntpdata->time_status |= STA_NANO;

        if (txc->modes & ADJ_MICRO)
                ntpdata->time_status &= ~STA_NANO;

        if (txc->modes & ADJ_FREQUENCY) {
                ntpdata->time_freq = txc->freq * PPM_SCALE;
                ntpdata->time_freq = min(ntpdata->time_freq, MAXFREQ_SCALED);
                ntpdata->time_freq = max(ntpdata->time_freq, -MAXFREQ_SCALED);
                /* Update pps_freq */
                pps_set_freq(ntpdata);
        }

        if (txc->modes & ADJ_MAXERROR)
                ntpdata->time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);

        if (txc->modes & ADJ_ESTERROR)
                ntpdata->time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);

        if (txc->modes & ADJ_TIMECONST) {
                ntpdata->time_constant = clamp(txc->constant, 0, MAXTC);
                if (!(ntpdata->time_status & STA_NANO))
                        ntpdata->time_constant += 4;
                ntpdata->time_constant = clamp(ntpdata->time_constant, 0, MAXTC);
        }

        if (txc->modes & ADJ_TAI && txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
                *time_tai = txc->constant;

        if (txc->modes & ADJ_OFFSET)
                ntp_update_offset(ntpdata, txc->offset);

        if (txc->modes & ADJ_TICK)
                ntpdata->tick_usec = txc->tick;

        if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
                ntp_update_frequency(ntpdata);
}

/*
 * adjtimex() mainly allows reading (and writing, if superuser) of
 * kernel time-keeping variables. used by xntpd.
 */
int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
                  s32 *time_tai, struct audit_ntp_data *ad)
{
        struct ntp_data *ntpdata = &tk_ntp_data;
        int result;

        if (txc->modes & ADJ_ADJTIME) {
                long save_adjust = ntpdata->time_adjust;

                if (!(txc->modes & ADJ_OFFSET_READONLY)) {
                        /* adjtime() is independent from ntp_adjtime() */
                        ntpdata->time_adjust = txc->offset;
                        ntp_update_frequency(ntpdata);

                        audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
                        audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, ntpdata->time_adjust);
                }
                txc->offset = save_adjust;
        } else {
                /* If there are input parameters, then process them: */
                if (txc->modes) {
                        audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, ntpdata->time_offset);
                        audit_ntp_set_old(ad, AUDIT_NTP_FREQ,   ntpdata->time_freq);
                        audit_ntp_set_old(ad, AUDIT_NTP_STATUS, ntpdata->time_status);
                        audit_ntp_set_old(ad, AUDIT_NTP_TAI,    *time_tai);
                        audit_ntp_set_old(ad, AUDIT_NTP_TICK,   ntpdata->tick_usec);

                        process_adjtimex_modes(ntpdata, txc, time_tai);

                        audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, ntpdata->time_offset);
                        audit_ntp_set_new(ad, AUDIT_NTP_FREQ,   ntpdata->time_freq);
                        audit_ntp_set_new(ad, AUDIT_NTP_STATUS, ntpdata->time_status);
                        audit_ntp_set_new(ad, AUDIT_NTP_TAI,    *time_tai);
                        audit_ntp_set_new(ad, AUDIT_NTP_TICK,   ntpdata->tick_usec);
                }

                txc->offset = shift_right(ntpdata->time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT);
                if (!(ntpdata->time_status & STA_NANO))
                        txc->offset = div_s64(txc->offset, NSEC_PER_USEC);
        }

        result = ntpdata->time_state;
        if (is_error_status(ntpdata->time_status))
                result = TIME_ERROR;

        txc->freq          = shift_right((ntpdata->time_freq >> PPM_SCALE_INV_SHIFT) *
                                         PPM_SCALE_INV, NTP_SCALE_SHIFT);
        txc->maxerror      = ntpdata->time_maxerror;
        txc->esterror      = ntpdata->time_esterror;
        txc->status        = ntpdata->time_status;
        txc->constant      = ntpdata->time_constant;
        txc->precision     = 1;
        txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
        txc->tick          = ntpdata->tick_usec;
        txc->tai           = *time_tai;

        /* Fill PPS status fields */
        pps_fill_timex(ntpdata, txc);

        txc->time.tv_sec = ts->tv_sec;
        txc->time.tv_usec = ts->tv_nsec;
        if (!(ntpdata->time_status & STA_NANO))
                txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;

        /* Handle leapsec adjustments */
        if (unlikely(ts->tv_sec >= ntpdata->ntp_next_leap_sec)) {
                if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS)) {
                        result = TIME_OOP;
                        txc->tai++;
                        txc->time.tv_sec--;
                }
                if ((ntpdata->time_state == TIME_DEL) && (ntpdata->time_status & STA_DEL)) {
                        result = TIME_WAIT;
                        txc->tai--;
                        txc->time.tv_sec++;
                }
                if ((ntpdata->time_state == TIME_OOP) && (ts->tv_sec == ntpdata->ntp_next_leap_sec))
                        result = TIME_WAIT;
        }

        return result;
}

#ifdef  CONFIG_NTP_PPS

/*
 * struct pps_normtime is basically a struct timespec, but it is
 * semantically different (and it is the reason why it was invented):
 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC)
 */
struct pps_normtime {
        s64             sec;    /* seconds */
        long            nsec;   /* nanoseconds */
};

/*
 * Normalize the timestamp so that nsec is in the
 * [ -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval
 */
static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
{
        struct pps_normtime norm = {
                .sec = ts.tv_sec,
                .nsec = ts.tv_nsec
        };

        if (norm.nsec > (NSEC_PER_SEC >> 1)) {
                norm.nsec -= NSEC_PER_SEC;
                norm.sec++;
        }

        return norm;
}

/* Get current phase correction and jitter */
static inline long pps_phase_filter_get(struct ntp_data *ntpdata, long *jitter)
{
        *jitter = ntpdata->pps_tf[0] - ntpdata->pps_tf[1];
        if (*jitter < 0)
                *jitter = -*jitter;

        /* TODO: test various filters */
        return ntpdata->pps_tf[0];
}

/* Add the sample to the phase filter */
static inline void pps_phase_filter_add(struct ntp_data *ntpdata, long err)
{
        ntpdata->pps_tf[2] = ntpdata->pps_tf[1];
        ntpdata->pps_tf[1] = ntpdata->pps_tf[0];
        ntpdata->pps_tf[0] = err;
}

/*
 * Decrease frequency calibration interval length. It is halved after four
 * consecutive unstable intervals.
 */
static inline void pps_dec_freq_interval(struct ntp_data *ntpdata)
{
        if (--ntpdata->pps_intcnt <= -PPS_INTCOUNT) {
                ntpdata->pps_intcnt = -PPS_INTCOUNT;
                if (ntpdata->pps_shift > PPS_INTMIN) {
                        ntpdata->pps_shift--;
                        ntpdata->pps_intcnt = 0;
                }
        }
}

/*
 * Increase frequency calibration interval length. It is doubled after
 * four consecutive stable intervals.
 */
static inline void pps_inc_freq_interval(struct ntp_data *ntpdata)
{
        if (++ntpdata->pps_intcnt >= PPS_INTCOUNT) {
                ntpdata->pps_intcnt = PPS_INTCOUNT;
                if (ntpdata->pps_shift < PPS_INTMAX) {
                        ntpdata->pps_shift++;
                        ntpdata->pps_intcnt = 0;
                }
        }
}

/*
 * Update clock frequency based on MONOTONIC_RAW clock PPS signal
 * timestamps
 *
 * At the end of the calibration interval the difference between the
 * first and last MONOTONIC_RAW clock timestamps divided by the length
 * of the interval becomes the frequency update. If the interval was
 * too long, the data are discarded.
 * Returns the difference between old and new frequency values.
 */
static long hardpps_update_freq(struct ntp_data *ntpdata, struct pps_normtime freq_norm)
{
        long delta, delta_mod;
        s64 ftemp;

        /* Check if the frequency interval was too long */
        if (freq_norm.sec > (2 << ntpdata->pps_shift)) {
                ntpdata->time_status |= STA_PPSERROR;
                ntpdata->pps_errcnt++;
                pps_dec_freq_interval(ntpdata);
                printk_deferred(KERN_ERR "hardpps: PPSERROR: interval too long - %lld s\n",
                                freq_norm.sec);
                return 0;
        }

        /*
         * Here the raw frequency offset and wander (stability) is
         * calculated. If the wander is less than the wander threshold the
         * interval is increased; otherwise it is decreased.
         */
        ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
                        freq_norm.sec);
        delta = shift_right(ftemp - ntpdata->pps_freq, NTP_SCALE_SHIFT);
        ntpdata->pps_freq = ftemp;
        if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
                printk_deferred(KERN_WARNING "hardpps: PPSWANDER: change=%ld\n", delta);
                ntpdata->time_status |= STA_PPSWANDER;
                ntpdata->pps_stbcnt++;
                pps_dec_freq_interval(ntpdata);
        } else {
                /* Good sample */
                pps_inc_freq_interval(ntpdata);
        }

        /*
         * The stability metric is calculated as the average of recent
         * frequency changes, but is used only for performance monitoring
         */
        delta_mod = delta;
        if (delta_mod < 0)
                delta_mod = -delta_mod;
        ntpdata->pps_stabil += (div_s64(((s64)delta_mod) << (NTP_SCALE_SHIFT - SHIFT_USEC),
                                     NSEC_PER_USEC) - ntpdata->pps_stabil) >> PPS_INTMIN;

        /* If enabled, the system clock frequency is updated */
        if ((ntpdata->time_status & STA_PPSFREQ) && !(ntpdata->time_status & STA_FREQHOLD)) {
                ntpdata->time_freq = ntpdata->pps_freq;
                ntp_update_frequency(ntpdata);
        }

        return delta;
}

/* Correct REALTIME clock phase error against PPS signal */
static void hardpps_update_phase(struct ntp_data *ntpdata, long error)
{
        long correction = -error;
        long jitter;

        /* Add the sample to the median filter */
        pps_phase_filter_add(ntpdata, correction);
        correction = pps_phase_filter_get(ntpdata, &jitter);

        /*
         * Nominal jitter is due to PPS signal noise. If it exceeds the
         * threshold, the sample is discarded; otherwise, if so enabled,
         * the time offset is updated.
         */
        if (jitter > (ntpdata->pps_jitter << PPS_POPCORN)) {
                printk_deferred(KERN_WARNING "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
                                jitter, (ntpdata->pps_jitter << PPS_POPCORN));
                ntpdata->time_status |= STA_PPSJITTER;
                ntpdata->pps_jitcnt++;
        } else if (ntpdata->time_status & STA_PPSTIME) {
                /* Correct the time using the phase offset */
                ntpdata->time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
                                               NTP_INTERVAL_FREQ);
                /* Cancel running adjtime() */
                ntpdata->time_adjust = 0;
        }
        /* Update jitter */
        ntpdata->pps_jitter += (jitter - ntpdata->pps_jitter) >> PPS_INTMIN;
}

/*
 * __hardpps() - discipline CPU clock oscillator to external PPS signal
 *
 * This routine is called at each PPS signal arrival in order to
 * discipline the CPU clock oscillator to the PPS signal. It takes two
 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 * is used to correct clock phase error and the latter is used to
 * correct the frequency.
 *
 * This code is based on David Mills's reference nanokernel
 * implementation. It was mostly rewritten but keeps the same idea.
 */
void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
{
        struct pps_normtime pts_norm, freq_norm;
        struct ntp_data *ntpdata = &tk_ntp_data;

        pts_norm = pps_normalize_ts(*phase_ts);

        /* Clear the error bits, they will be set again if needed */
        ntpdata->time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);

        /* indicate signal presence */
        ntpdata->time_status |= STA_PPSSIGNAL;
        ntpdata->pps_valid = PPS_VALID;

        /*
         * When called for the first time, just start the frequency
         * interval
         */
        if (unlikely(ntpdata->pps_fbase.tv_sec == 0)) {
                ntpdata->pps_fbase = *raw_ts;
                return;
        }

        /* Ok, now we have a base for frequency calculation */
        freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, ntpdata->pps_fbase));

        /*
         * Check that the signal is in the range
         * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it
         */
        if ((freq_norm.sec == 0) || (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
            (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
                ntpdata->time_status |= STA_PPSJITTER;
                /* Restart the frequency calibration interval */
                ntpdata->pps_fbase = *raw_ts;
                printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
                return;
        }

        /* Signal is ok. Check if the current frequency interval is finished */
        if (freq_norm.sec >= (1 << ntpdata->pps_shift)) {
                ntpdata->pps_calcnt++;
                /* Restart the frequency calibration interval */
                ntpdata->pps_fbase = *raw_ts;
                hardpps_update_freq(ntpdata, freq_norm);
        }

        hardpps_update_phase(ntpdata, pts_norm.nsec);

}
#endif  /* CONFIG_NTP_PPS */

static int __init ntp_tick_adj_setup(char *str)
{
        int rc = kstrtos64(str, 0, &tk_ntp_data.ntp_tick_adj);
        if (rc)
                return rc;

        tk_ntp_data.ntp_tick_adj <<= NTP_SCALE_SHIFT;
        return 1;
}

__setup("ntp_tick_adj=", ntp_tick_adj_setup);

void __init ntp_init(void)
{
        ntp_clear();
        ntp_init_cmos_sync();
}