// SPDX-License-Identifier: GPL-2.0
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/*
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* NTP state machine interfaces and logic.
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*
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* This code was mainly moved from kernel/timer.c and kernel/time.c
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* Please see those files for relevant copyright info and historical
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* changelogs.
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*/
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#include <linux/capability.h>
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#include <linux/clocksource.h>
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#include <linux/workqueue.h>
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#include <linux/hrtimer.h>
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#include <linux/jiffies.h>
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#include <linux/math64.h>
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#include <linux/timex.h>
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#include <linux/time.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/rtc.h>
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#include <linux/audit.h>
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#include "ntp_internal.h"
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#include "timekeeping_internal.h"
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/*
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* NTP timekeeping variables:
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*
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* Note: All of the NTP state is protected by the timekeeping locks.
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*/
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/* USER_HZ period (usecs): */
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unsigned long tick_usec = USER_TICK_USEC;
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/* SHIFTED_HZ period (nsecs): */
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unsigned long tick_nsec;
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static u64 tick_length;
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static u64 tick_length_base;
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#define SECS_PER_DAY 86400
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#define MAX_TICKADJ 500LL /* usecs */
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#define MAX_TICKADJ_SCALED \
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(((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
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#define MAX_TAI_OFFSET 100000
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/*
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* phase-lock loop variables
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*/
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/*
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* clock synchronization status
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*
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* (TIME_ERROR prevents overwriting the CMOS clock)
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*/
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static int time_state = TIME_OK;
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/* clock status bits: */
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static int time_status = STA_UNSYNC;
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/* time adjustment (nsecs): */
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static s64 time_offset;
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/* pll time constant: */
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static long time_constant = 2;
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/* maximum error (usecs): */
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static long time_maxerror = NTP_PHASE_LIMIT;
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/* estimated error (usecs): */
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static long time_esterror = NTP_PHASE_LIMIT;
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/* frequency offset (scaled nsecs/secs): */
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static s64 time_freq;
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/* time at last adjustment (secs): */
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static time64_t time_reftime;
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static long time_adjust;
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/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
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static s64 ntp_tick_adj;
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/* second value of the next pending leapsecond, or TIME64_MAX if no leap */
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static time64_t ntp_next_leap_sec = TIME64_MAX;
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#ifdef CONFIG_NTP_PPS
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/*
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* The following variables are used when a pulse-per-second (PPS) signal
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* is available. They establish the engineering parameters of the clock
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* discipline loop when controlled by the PPS signal.
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*/
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#define PPS_VALID 10 /* PPS signal watchdog max (s) */
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#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
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#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
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#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
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#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
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increase pps_shift or consecutive bad
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intervals to decrease it */
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#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
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static int pps_valid; /* signal watchdog counter */
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static long pps_tf[3]; /* phase median filter */
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static long pps_jitter; /* current jitter (ns) */
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static struct timespec64 pps_fbase; /* beginning of the last freq interval */
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static int pps_shift; /* current interval duration (s) (shift) */
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static int pps_intcnt; /* interval counter */
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static s64 pps_freq; /* frequency offset (scaled ns/s) */
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static long pps_stabil; /* current stability (scaled ns/s) */
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/*
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* PPS signal quality monitors
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*/
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static long pps_calcnt; /* calibration intervals */
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static long pps_jitcnt; /* jitter limit exceeded */
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static long pps_stbcnt; /* stability limit exceeded */
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static long pps_errcnt; /* calibration errors */
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|
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/* PPS kernel consumer compensates the whole phase error immediately.
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* Otherwise, reduce the offset by a fixed factor times the time constant.
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*/
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static inline s64 ntp_offset_chunk(s64 offset)
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{
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if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
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return offset;
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else
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return shift_right(offset, SHIFT_PLL + time_constant);
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}
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static inline void pps_reset_freq_interval(void)
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{
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/* the PPS calibration interval may end
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surprisingly early */
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pps_shift = PPS_INTMIN;
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pps_intcnt = 0;
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}
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/**
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* pps_clear - Clears the PPS state variables
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*/
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static inline void pps_clear(void)
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{
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pps_reset_freq_interval();
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pps_tf[0] = 0;
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pps_tf[1] = 0;
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pps_tf[2] = 0;
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pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
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pps_freq = 0;
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}
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/* Decrease pps_valid to indicate that another second has passed since
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* the last PPS signal. When it reaches 0, indicate that PPS signal is
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* missing.
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*/
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static inline void pps_dec_valid(void)
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{
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if (pps_valid > 0)
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pps_valid--;
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else {
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time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
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STA_PPSWANDER | STA_PPSERROR);
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pps_clear();
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}
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}
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static inline void pps_set_freq(s64 freq)
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{
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pps_freq = freq;
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}
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static inline int is_error_status(int status)
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{
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return (status & (STA_UNSYNC|STA_CLOCKERR))
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/* PPS signal lost when either PPS time or
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* PPS frequency synchronization requested
|
*/
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|| ((status & (STA_PPSFREQ|STA_PPSTIME))
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&& !(status & STA_PPSSIGNAL))
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/* PPS jitter exceeded when
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* PPS time synchronization requested */
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|| ((status & (STA_PPSTIME|STA_PPSJITTER))
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== (STA_PPSTIME|STA_PPSJITTER))
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/* PPS wander exceeded or calibration error when
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* PPS frequency synchronization requested
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*/
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|| ((status & STA_PPSFREQ)
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&& (status & (STA_PPSWANDER|STA_PPSERROR)));
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}
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static inline void pps_fill_timex(struct __kernel_timex *txc)
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{
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txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
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PPM_SCALE_INV, NTP_SCALE_SHIFT);
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txc->jitter = pps_jitter;
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if (!(time_status & STA_NANO))
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txc->jitter = pps_jitter / NSEC_PER_USEC;
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txc->shift = pps_shift;
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txc->stabil = pps_stabil;
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txc->jitcnt = pps_jitcnt;
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txc->calcnt = pps_calcnt;
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txc->errcnt = pps_errcnt;
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txc->stbcnt = pps_stbcnt;
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}
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#else /* !CONFIG_NTP_PPS */
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static inline s64 ntp_offset_chunk(s64 offset)
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{
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return shift_right(offset, SHIFT_PLL + time_constant);
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}
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static inline void pps_reset_freq_interval(void) {}
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static inline void pps_clear(void) {}
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static inline void pps_dec_valid(void) {}
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static inline void pps_set_freq(s64 freq) {}
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static inline int is_error_status(int status)
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{
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return status & (STA_UNSYNC|STA_CLOCKERR);
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}
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static inline void pps_fill_timex(struct __kernel_timex *txc)
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{
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/* PPS is not implemented, so these are zero */
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txc->ppsfreq = 0;
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txc->jitter = 0;
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txc->shift = 0;
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txc->stabil = 0;
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txc->jitcnt = 0;
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txc->calcnt = 0;
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txc->errcnt = 0;
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txc->stbcnt = 0;
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}
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#endif /* CONFIG_NTP_PPS */
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|
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/**
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* ntp_synced - Returns 1 if the NTP status is not UNSYNC
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*
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*/
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static inline int ntp_synced(void)
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{
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return !(time_status & STA_UNSYNC);
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}
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/*
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* NTP methods:
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*/
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/*
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* Update (tick_length, tick_length_base, tick_nsec), based
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* on (tick_usec, ntp_tick_adj, time_freq):
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*/
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static void ntp_update_frequency(void)
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{
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u64 second_length;
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u64 new_base;
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second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
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<< NTP_SCALE_SHIFT;
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second_length += ntp_tick_adj;
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second_length += time_freq;
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tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
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new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
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/*
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* Don't wait for the next second_overflow, apply
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* the change to the tick length immediately:
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*/
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tick_length += new_base - tick_length_base;
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tick_length_base = new_base;
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}
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static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
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{
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time_status &= ~STA_MODE;
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if (secs < MINSEC)
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return 0;
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if (!(time_status & STA_FLL) && (secs <= MAXSEC))
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return 0;
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time_status |= STA_MODE;
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return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
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}
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static void ntp_update_offset(long offset)
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{
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s64 freq_adj;
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s64 offset64;
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long secs;
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if (!(time_status & STA_PLL))
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return;
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if (!(time_status & STA_NANO)) {
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/* Make sure the multiplication below won't overflow */
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offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
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offset *= NSEC_PER_USEC;
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}
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/*
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* Scale the phase adjustment and
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* clamp to the operating range.
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*/
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offset = clamp(offset, -MAXPHASE, MAXPHASE);
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/*
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* Select how the frequency is to be controlled
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* and in which mode (PLL or FLL).
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*/
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secs = (long)(__ktime_get_real_seconds() - time_reftime);
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if (unlikely(time_status & STA_FREQHOLD))
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secs = 0;
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time_reftime = __ktime_get_real_seconds();
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offset64 = offset;
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freq_adj = ntp_update_offset_fll(offset64, secs);
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/*
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* Clamp update interval to reduce PLL gain with low
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* sampling rate (e.g. intermittent network connection)
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* to avoid instability.
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*/
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if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
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secs = 1 << (SHIFT_PLL + 1 + time_constant);
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freq_adj += (offset64 * secs) <<
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(NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
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freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
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time_freq = max(freq_adj, -MAXFREQ_SCALED);
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time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
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}
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/**
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* ntp_clear - Clears the NTP state variables
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*/
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void ntp_clear(void)
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{
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time_adjust = 0; /* stop active adjtime() */
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time_status |= STA_UNSYNC;
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time_maxerror = NTP_PHASE_LIMIT;
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time_esterror = NTP_PHASE_LIMIT;
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ntp_update_frequency();
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tick_length = tick_length_base;
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time_offset = 0;
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ntp_next_leap_sec = TIME64_MAX;
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/* Clear PPS state variables */
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pps_clear();
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}
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u64 ntp_tick_length(void)
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{
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return tick_length;
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}
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/**
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* 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.
|
*/
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ktime_t ntp_get_next_leap(void)
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{
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ktime_t ret;
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if ((time_state == TIME_INS) && (time_status & STA_INS))
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return ktime_set(ntp_next_leap_sec, 0);
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ret = KTIME_MAX;
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return ret;
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}
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|
/*
|
* 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)
|
{
|
s64 delta;
|
int leap = 0;
|
s32 rem;
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|
/*
|
* 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) {
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case TIME_OK:
|
if (time_status & STA_INS) {
|
time_state = TIME_INS;
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div_s64_rem(secs, SECS_PER_DAY, &rem);
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ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
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} else if (time_status & STA_DEL) {
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time_state = TIME_DEL;
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div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
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ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
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}
|
break;
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case TIME_INS:
|
if (!(time_status & STA_INS)) {
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ntp_next_leap_sec = TIME64_MAX;
|
time_state = TIME_OK;
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} else if (secs == ntp_next_leap_sec) {
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leap = -1;
|
time_state = TIME_OOP;
|
printk(KERN_NOTICE
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"Clock: inserting leap second 23:59:60 UTC\n");
|
}
|
break;
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case TIME_DEL:
|
if (!(time_status & STA_DEL)) {
|
ntp_next_leap_sec = TIME64_MAX;
|
time_state = TIME_OK;
|
} else if (secs == ntp_next_leap_sec) {
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leap = 1;
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ntp_next_leap_sec = TIME64_MAX;
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time_state = TIME_WAIT;
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printk(KERN_NOTICE
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"Clock: deleting leap second 23:59:59 UTC\n");
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}
|
break;
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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) {
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time_maxerror = NTP_PHASE_LIMIT;
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time_status |= STA_UNSYNC;
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}
|
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/* Compute the phase adjustment for the next second */
|
tick_length = tick_length_base;
|
|
delta = ntp_offset_chunk(time_offset);
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time_offset -= delta;
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tick_length += delta;
|
|
/* Check PPS signal */
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pps_dec_valid();
|
|
if (!time_adjust)
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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)
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<< NTP_SCALE_SHIFT;
|
time_adjust = 0;
|
|
out:
|
return leap;
|
}
|
|
static void sync_hw_clock(struct work_struct *work);
|
static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock);
|
|
static void sched_sync_hw_clock(struct timespec64 now,
|
unsigned long target_nsec, bool fail)
|
|
{
|
struct timespec64 next;
|
|
ktime_get_real_ts64(&next);
|
if (!fail)
|
next.tv_sec = 659;
|
else {
|
/*
|
* Try again as soon as possible. Delaying long periods
|
* decreases the accuracy of the work queue timer. Due to this
|
* the algorithm is very likely to require a short-sleep retry
|
* after the above long sleep to synchronize ts_nsec.
|
*/
|
next.tv_sec = 0;
|
}
|
|
/* Compute the needed delay that will get to tv_nsec == target_nsec */
|
next.tv_nsec = target_nsec - next.tv_nsec;
|
if (next.tv_nsec <= 0)
|
next.tv_nsec += NSEC_PER_SEC;
|
if (next.tv_nsec >= NSEC_PER_SEC) {
|
next.tv_sec++;
|
next.tv_nsec -= NSEC_PER_SEC;
|
}
|
|
queue_delayed_work(system_power_efficient_wq, &sync_work,
|
timespec64_to_jiffies(&next));
|
}
|
|
static void sync_rtc_clock(void)
|
{
|
unsigned long target_nsec;
|
struct timespec64 adjust, now;
|
int rc;
|
|
if (!IS_ENABLED(CONFIG_RTC_SYSTOHC))
|
return;
|
|
ktime_get_real_ts64(&now);
|
|
adjust = now;
|
if (persistent_clock_is_local)
|
adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
|
|
/*
|
* The current RTC in use will provide the target_nsec it wants to be
|
* called at, and does rtc_tv_nsec_ok internally.
|
*/
|
rc = rtc_set_ntp_time(adjust, &target_nsec);
|
if (rc == -ENODEV)
|
return;
|
|
sched_sync_hw_clock(now, target_nsec, rc);
|
}
|
|
#ifdef CONFIG_GENERIC_CMOS_UPDATE
|
int __weak update_persistent_clock64(struct timespec64 now64)
|
{
|
return -ENODEV;
|
}
|
#endif
|
|
static bool sync_cmos_clock(void)
|
{
|
static bool no_cmos;
|
struct timespec64 now;
|
struct timespec64 adjust;
|
int rc = -EPROTO;
|
long target_nsec = NSEC_PER_SEC / 2;
|
|
if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE))
|
return false;
|
|
if (no_cmos)
|
return false;
|
|
/*
|
* Historically update_persistent_clock64() has followed x86
|
* semantics, which match the MC146818A/etc RTC. This RTC will store
|
* 'adjust' and then in .5s it will advance once second.
|
*
|
* Architectures are strongly encouraged to use rtclib and not
|
* implement this legacy API.
|
*/
|
ktime_get_real_ts64(&now);
|
if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) {
|
if (persistent_clock_is_local)
|
adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
|
rc = update_persistent_clock64(adjust);
|
/*
|
* The machine does not support update_persistent_clock64 even
|
* though it defines CONFIG_GENERIC_CMOS_UPDATE.
|
*/
|
if (rc == -ENODEV) {
|
no_cmos = true;
|
return false;
|
}
|
}
|
|
sched_sync_hw_clock(now, target_nsec, rc);
|
return true;
|
}
|
|
/*
|
* 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)
|
{
|
if (!ntp_synced())
|
return;
|
|
if (sync_cmos_clock())
|
return;
|
|
sync_rtc_clock();
|
}
|
|
void ntp_notify_cmos_timer(void)
|
{
|
if (!ntp_synced())
|
return;
|
|
if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) ||
|
IS_ENABLED(CONFIG_RTC_SYSTOHC))
|
queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
|
}
|
|
/*
|
* Propagate a new txc->status value into the NTP state:
|
*/
|
static inline void process_adj_status(const struct __kernel_timex *txc)
|
{
|
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 = __ktime_get_real_seconds();
|
|
/* only set allowed bits */
|
time_status &= STA_RONLY;
|
time_status |= txc->status & ~STA_RONLY;
|
}
|
|
|
static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
|
s32 *time_tai)
|
{
|
if (txc->modes & ADJ_STATUS)
|
process_adj_status(txc);
|
|
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 && txc->constant <= MAX_TAI_OFFSET)
|
*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();
|
}
|
|
|
/*
|
* 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)
|
{
|
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();
|
|
audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
|
audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, 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, time_offset);
|
audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq);
|
audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status);
|
audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai);
|
audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec);
|
|
process_adjtimex_modes(txc, time_tai);
|
|
audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset);
|
audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq);
|
audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status);
|
audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai);
|
audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec);
|
}
|
|
txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
|
NTP_SCALE_SHIFT);
|
if (!(time_status & STA_NANO))
|
txc->offset = (u32)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 = ts->tv_sec;
|
txc->time.tv_usec = ts->tv_nsec;
|
if (!(time_status & STA_NANO))
|
txc->time.tv_usec = ts->tv_nsec / 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 = kstrtos64(str, 0, &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();
|
}
|
