/* * 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 #include #include #include #include #include #include #include #include #include #include #include "ntp_internal.h" /* * NTP timekeeping variables: * * Note: All of the NTP state is protected by the timekeeping locks. */ /* USER_HZ period (usecs): */ unsigned long tick_usec = TICK_USEC; /* SHIFTED_HZ period (nsecs): */ unsigned long tick_nsec; static u64 tick_length; static u64 tick_length_base; #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) /* * phase-lock loop variables */ /* * clock synchronization status * * (TIME_ERROR prevents overwriting the CMOS clock) */ static int time_state = TIME_OK; /* clock status bits: */ static int time_status = STA_UNSYNC; /* time adjustment (nsecs): */ static s64 time_offset; /* pll time constant: */ static long time_constant = 2; /* maximum error (usecs): */ static long time_maxerror = NTP_PHASE_LIMIT; /* estimated error (usecs): */ static long time_esterror = NTP_PHASE_LIMIT; /* frequency offset (scaled nsecs/secs): */ static s64 time_freq; /* time at last adjustment (secs): */ static long time_reftime; static long time_adjust; /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ static s64 ntp_tick_adj; /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ static time64_t ntp_next_leap_sec = TIME64_MAX; #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) */ static int pps_valid; /* signal watchdog counter */ static long pps_tf[3]; /* phase median filter */ static long pps_jitter; /* current jitter (ns) */ static struct timespec64 pps_fbase; /* beginning of the last freq interval */ static int pps_shift; /* current interval duration (s) (shift) */ static int pps_intcnt; /* interval counter */ static s64 pps_freq; /* frequency offset (scaled ns/s) */ static long pps_stabil; /* current stability (scaled ns/s) */ /* * PPS signal quality monitors */ static long pps_calcnt; /* calibration intervals */ static long pps_jitcnt; /* jitter limit exceeded */ static long pps_stbcnt; /* stability limit exceeded */ static long pps_errcnt; /* calibration errors */ /* 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(s64 offset) { if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) return offset; else return shift_right(offset, SHIFT_PLL + time_constant); } static inline void pps_reset_freq_interval(void) { /* the PPS calibration interval may end surprisingly early */ pps_shift = PPS_INTMIN; pps_intcnt = 0; } /** * pps_clear - Clears the PPS state variables */ static inline void pps_clear(void) { pps_reset_freq_interval(); pps_tf[0] = 0; pps_tf[1] = 0; pps_tf[2] = 0; pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 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(void) { if (pps_valid > 0) pps_valid--; else { time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); pps_clear(); } } static inline void pps_set_freq(s64 freq) { pps_freq = freq; } static inline int 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 timex *txc) { txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * PPM_SCALE_INV, NTP_SCALE_SHIFT); txc->jitter = pps_jitter; if (!(time_status & STA_NANO)) txc->jitter /= NSEC_PER_USEC; txc->shift = pps_shift; txc->stabil = pps_stabil; txc->jitcnt = pps_jitcnt; txc->calcnt = pps_calcnt; txc->errcnt = pps_errcnt; txc->stbcnt = pps_stbcnt; } #else /* !CONFIG_NTP_PPS */ static inline s64 ntp_offset_chunk(s64 offset) { return shift_right(offset, SHIFT_PLL + time_constant); } static inline void pps_reset_freq_interval(void) {} static inline void pps_clear(void) {} static inline void pps_dec_valid(void) {} static inline void pps_set_freq(s64 freq) {} static inline int is_error_status(int status) { return status & (STA_UNSYNC|STA_CLOCKERR); } static inline void pps_fill_timex(struct 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 */ /** * ntp_synced - Returns 1 if the NTP status is not UNSYNC * */ static inline int ntp_synced(void) { return !(time_status & STA_UNSYNC); } /* * NTP methods: */ /* * Update (tick_length, tick_length_base, tick_nsec), based * on (tick_usec, ntp_tick_adj, time_freq): */ static void ntp_update_frequency(void) { u64 second_length; u64 new_base; second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT; second_length += ntp_tick_adj; second_length += time_freq; tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 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: */ tick_length += new_base - tick_length_base; tick_length_base = new_base; } static inline s64 ntp_update_offset_fll(s64 offset64, long secs) { time_status &= ~STA_MODE; if (secs < MINSEC) return 0; if (!(time_status & STA_FLL) && (secs <= MAXSEC)) return 0; time_status |= STA_MODE; return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); } static void ntp_update_offset(long offset) { s64 freq_adj; s64 offset64; long secs; if (!(time_status & STA_PLL)) return; if (!(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). */ secs = get_seconds() - time_reftime; if (unlikely(time_status & STA_FREQHOLD)) secs = 0; time_reftime = get_seconds(); offset64 = offset; freq_adj = ntp_update_offset_fll(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 + time_constant))) secs = 1 << (SHIFT_PLL + 1 + time_constant); freq_adj += (offset64 * secs) << (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); time_freq = max(freq_adj, -MAXFREQ_SCALED); time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); } /** * ntp_clear - Clears the NTP state variables */ 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; ntp_next_leap_sec = TIME64_MAX; /* Clear PPS state variables */ pps_clear(); } u64 ntp_tick_length(void) { return 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) { ktime_t ret; if ((time_state == TIME_INS) && (time_status & STA_INS)) return ktime_set(ntp_next_leap_sec, 0); ret.tv64 = 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(unsigned long secs) { s64 delta; int leap = 0; /* * 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 (time_state) { case TIME_OK: if (time_status & STA_INS) { time_state = TIME_INS; ntp_next_leap_sec = secs + SECS_PER_DAY - (secs % SECS_PER_DAY); } else if (time_status & STA_DEL) { time_state = TIME_DEL; ntp_next_leap_sec = secs + SECS_PER_DAY - ((secs+1) % SECS_PER_DAY); } break; case TIME_INS: if (!(time_status & STA_INS)) { ntp_next_leap_sec = TIME64_MAX; time_state = TIME_OK; } else if (secs % SECS_PER_DAY == 0) { leap = -1; time_state = TIME_OOP; printk(KERN_NOTICE "Clock: inserting leap second 23:59:60 UTC\n"); } break; case TIME_DEL: if (!(time_status & STA_DEL)) { ntp_next_leap_sec = TIME64_MAX; time_state = TIME_OK; } else if ((secs + 1) % SECS_PER_DAY == 0) { leap = 1; ntp_next_leap_sec = TIME64_MAX; time_state = TIME_WAIT; printk(KERN_NOTICE "Clock: deleting leap second 23:59:59 UTC\n"); } break; case TIME_OOP: ntp_next_leap_sec = TIME64_MAX; time_state = TIME_WAIT; break; case TIME_WAIT: if (!(time_status & (STA_INS | STA_DEL))) time_state = TIME_OK; break; } /* Bump the maxerror field */ time_maxerror += MAXFREQ / NSEC_PER_USEC; if (time_maxerror > NTP_PHASE_LIMIT) { time_maxerror = NTP_PHASE_LIMIT; time_status |= STA_UNSYNC; } /* Compute the phase adjustment for the next second */ tick_length = tick_length_base; delta = ntp_offset_chunk(time_offset); time_offset -= delta; tick_length += delta; /* Check PPS signal */ pps_dec_valid(); if (!time_adjust) goto out; if (time_adjust > MAX_TICKADJ) { time_adjust -= MAX_TICKADJ; tick_length += MAX_TICKADJ_SCALED; goto out; } if (time_adjust < -MAX_TICKADJ) { time_adjust += MAX_TICKADJ; tick_length -= MAX_TICKADJ_SCALED; goto out; } tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT; time_adjust = 0; out: return leap; } #ifdef CONFIG_GENERIC_CMOS_UPDATE int __weak update_persistent_clock(struct timespec now) { return -ENODEV; } int __weak update_persistent_clock64(struct timespec64 now64) { struct timespec now; now = timespec64_to_timespec(now64); return update_persistent_clock(now); } #endif #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) static void sync_cmos_clock(struct work_struct *work); static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); static void sync_cmos_clock(struct work_struct *work) { struct timespec64 now; struct timespec64 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... * We want the clock to be within a couple of ticks from the target. */ if (!ntp_synced()) { /* * Not synced, exit, do not restart a timer (if one is * running, let it run out). */ return; } getnstimeofday64(&now); if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { struct timespec64 adjust = now; fail = -ENODEV; if (persistent_clock_is_local) adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); #ifdef CONFIG_GENERIC_CMOS_UPDATE fail = update_persistent_clock64(adjust); #endif #ifdef CONFIG_RTC_SYSTOHC if (fail == -ENODEV) fail = rtc_set_ntp_time(adjust); #endif } next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); if (next.tv_nsec <= 0) next.tv_nsec += NSEC_PER_SEC; if (!fail || fail == -ENODEV) 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; } queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, timespec64_to_jiffies(&next)); } void ntp_notify_cmos_timer(void) { queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); } #else void ntp_notify_cmos_timer(void) { } #endif /* * Propagate a new txc->status value into the NTP state: */ static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) { if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { time_state = TIME_OK; time_status = STA_UNSYNC; ntp_next_leap_sec = TIME64_MAX; /* restart PPS frequency calibration */ pps_reset_freq_interval(); } /* * If we turn on PLL adjustments then reset the * reference time to current time. */ if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) time_reftime = get_seconds(); /* only set allowed bits */ time_status &= STA_RONLY; time_status |= txc->status & ~STA_RONLY; } static inline void process_adjtimex_modes(struct timex *txc, struct timespec64 *ts, s32 *time_tai) { if (txc->modes & ADJ_STATUS) process_adj_status(txc, ts); if (txc->modes & ADJ_NANO) time_status |= STA_NANO; if (txc->modes & ADJ_MICRO) time_status &= ~STA_NANO; if (txc->modes & ADJ_FREQUENCY) { time_freq = txc->freq * PPM_SCALE; time_freq = min(time_freq, MAXFREQ_SCALED); time_freq = max(time_freq, -MAXFREQ_SCALED); /* update pps_freq */ pps_set_freq(time_freq); } if (txc->modes & ADJ_MAXERROR) time_maxerror = txc->maxerror; if (txc->modes & ADJ_ESTERROR) time_esterror = txc->esterror; if (txc->modes & ADJ_TIMECONST) { time_constant = txc->constant; if (!(time_status & STA_NANO)) time_constant += 4; time_constant = min(time_constant, (long)MAXTC); time_constant = max(time_constant, 0l); } if (txc->modes & ADJ_TAI && txc->constant > 0) *time_tai = txc->constant; if (txc->modes & ADJ_OFFSET) ntp_update_offset(txc->offset); if (txc->modes & ADJ_TICK) tick_usec = txc->tick; if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) ntp_update_frequency(); } /** * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex */ int ntp_validate_timex(struct timex *txc) { if (txc->modes & ADJ_ADJTIME) { /* singleshot must not be used with any other mode bits */ if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) return -EINVAL; if (!(txc->modes & ADJ_OFFSET_READONLY) && !capable(CAP_SYS_TIME)) return -EPERM; } else { /* In order to modify anything, you gotta be super-user! */ if (txc->modes && !capable(CAP_SYS_TIME)) return -EPERM; /* * if the quartz is off by more than 10% then * something is VERY wrong! */ if (txc->modes & ADJ_TICK && (txc->tick < 900000/USER_HZ || txc->tick > 1100000/USER_HZ)) return -EINVAL; } if (txc->modes & ADJ_SETOFFSET) { /* In order to inject time, you gotta be super-user! */ if (!capable(CAP_SYS_TIME)) return -EPERM; if (!timeval_inject_offset_valid(&txc->time)) return -EINVAL; } /* * Check for potential multiplication overflows that can * only happen on 64-bit systems: */ if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { if (LLONG_MIN / PPM_SCALE > txc->freq) return -EINVAL; if (LLONG_MAX / PPM_SCALE < txc->freq) return -EINVAL; } return 0; } /* * adjtimex mainly allows reading (and writing, if superuser) of * kernel time-keeping variables. used by xntpd. */ int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) { int result; if (txc->modes & ADJ_ADJTIME) { long save_adjust = time_adjust; if (!(txc->modes & ADJ_OFFSET_READONLY)) { /* adjtime() is independent from ntp_adjtime() */ time_adjust = txc->offset; ntp_update_frequency(); } txc->offset = save_adjust; } else { /* If there are input parameters, then process them: */ if (txc->modes) process_adjtimex_modes(txc, ts, time_tai); txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT); if (!(time_status & STA_NANO)) txc->offset /= NSEC_PER_USEC; } result = time_state; /* mostly `TIME_OK' */ /* check for errors */ if (is_error_status(time_status)) result = TIME_ERROR; txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * PPM_SCALE_INV, NTP_SCALE_SHIFT); txc->maxerror = time_maxerror; txc->esterror = time_esterror; txc->status = time_status; txc->constant = time_constant; txc->precision = 1; txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; txc->tick = tick_usec; txc->tai = *time_tai; /* fill PPS status fields */ pps_fill_timex(txc); txc->time.tv_sec = (time_t)ts->tv_sec; txc->time.tv_usec = ts->tv_nsec; if (!(time_status & STA_NANO)) txc->time.tv_usec /= NSEC_PER_USEC; /* Handle leapsec adjustments */ if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { if ((time_state == TIME_INS) && (time_status & STA_INS)) { result = TIME_OOP; txc->tai++; txc->time.tv_sec--; } if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { result = TIME_WAIT; txc->tai--; txc->time.tv_sec++; } if ((time_state == TIME_OOP) && (ts->tv_sec == ntp_next_leap_sec)) { result = TIME_WAIT; } } return result; } #ifdef CONFIG_NTP_PPS /* actually struct pps_normtime is good old 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(long *jitter) { *jitter = pps_tf[0] - pps_tf[1]; if (*jitter < 0) *jitter = -*jitter; /* TODO: test various filters */ return pps_tf[0]; } /* add the sample to the phase filter */ static inline void pps_phase_filter_add(long err) { pps_tf[2] = pps_tf[1]; pps_tf[1] = pps_tf[0]; pps_tf[0] = err; } /* decrease frequency calibration interval length. * It is halved after four consecutive unstable intervals. */ static inline void pps_dec_freq_interval(void) { if (--pps_intcnt <= -PPS_INTCOUNT) { pps_intcnt = -PPS_INTCOUNT; if (pps_shift > PPS_INTMIN) { pps_shift--; pps_intcnt = 0; } } } /* increase frequency calibration interval length. * It is doubled after four consecutive stable intervals. */ static inline void pps_inc_freq_interval(void) { if (++pps_intcnt >= PPS_INTCOUNT) { pps_intcnt = PPS_INTCOUNT; if (pps_shift < PPS_INTMAX) { pps_shift++; 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 pps_normtime freq_norm) { long delta, delta_mod; s64 ftemp; /* check if the frequency interval was too long */ if (freq_norm.sec > (2 << pps_shift)) { time_status |= STA_PPSERROR; pps_errcnt++; pps_dec_freq_interval(); 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 - pps_freq, NTP_SCALE_SHIFT); pps_freq = ftemp; if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { printk_deferred(KERN_WARNING "hardpps: PPSWANDER: change=%ld\n", delta); time_status |= STA_PPSWANDER; pps_stbcnt++; pps_dec_freq_interval(); } else { /* good sample */ pps_inc_freq_interval(); } /* 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; pps_stabil += (div_s64(((s64)delta_mod) << (NTP_SCALE_SHIFT - SHIFT_USEC), NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; /* if enabled, the system clock frequency is updated */ if ((time_status & STA_PPSFREQ) != 0 && (time_status & STA_FREQHOLD) == 0) { time_freq = pps_freq; ntp_update_frequency(); } return delta; } /* correct REALTIME clock phase error against PPS signal */ static void hardpps_update_phase(long error) { long correction = -error; long jitter; /* add the sample to the median filter */ pps_phase_filter_add(correction); correction = pps_phase_filter_get(&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 > (pps_jitter << PPS_POPCORN)) { printk_deferred(KERN_WARNING "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", jitter, (pps_jitter << PPS_POPCORN)); time_status |= STA_PPSJITTER; pps_jitcnt++; } else if (time_status & STA_PPSTIME) { /* correct the time using the phase offset */ time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); /* cancel running adjtime() */ time_adjust = 0; } /* update jitter */ pps_jitter += (jitter - 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; pts_norm = pps_normalize_ts(*phase_ts); /* clear the error bits, they will be set again if needed */ time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); /* indicate signal presence */ time_status |= STA_PPSSIGNAL; pps_valid = PPS_VALID; /* when called for the first time, * just start the frequency interval */ if (unlikely(pps_fbase.tv_sec == 0)) { pps_fbase = *raw_ts; return; } /* ok, now we have a base for frequency calculation */ freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, 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)) { time_status |= STA_PPSJITTER; /* restart the frequency calibration interval */ 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 << pps_shift)) { pps_calcnt++; /* restart the frequency calibration interval */ pps_fbase = *raw_ts; hardpps_update_freq(freq_norm); } hardpps_update_phase(pts_norm.nsec); } #endif /* CONFIG_NTP_PPS */ static int __init ntp_tick_adj_setup(char *str) { int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); if (rc) return rc; ntp_tick_adj <<= NTP_SCALE_SHIFT; return 1; } __setup("ntp_tick_adj=", ntp_tick_adj_setup); void __init ntp_init(void) { ntp_clear(); }