linux/kernel/time/ntp.c
Linus Torvalds 2bcc673101 Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
 "Yet another big pile of changes:

   - More year 2038 work from Arnd slowly reaching the point where we
     need to think about the syscalls themself.

   - A new timer function which allows to conditionally (re)arm a timer
     only when it's either not running or the new expiry time is sooner
     than the armed expiry time. This allows to use a single timer for
     multiple timeout requirements w/o caring about the first expiry
     time at the call site.

   - A new NMI safe accessor to clock real time for the printk timestamp
     work. Can be used by tracing, perf as well if required.

   - A large number of timer setup conversions from Kees which got
     collected here because either maintainers requested so or they
     simply got ignored. As Kees pointed out already there are a few
     trivial merge conflicts and some redundant commits which was
     unavoidable due to the size of this conversion effort.

   - Avoid a redundant iteration in the timer wheel softirq processing.

   - Provide a mechanism to treat RTC implementations depending on their
     hardware properties, i.e. don't inflict the write at the 0.5
     seconds boundary which originates from the PC CMOS RTC to all RTCs.
     No functional change as drivers need to be updated separately.

   - The usual small updates to core code clocksource drivers. Nothing
     really exciting"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  timers: Add a function to start/reduce a timer
  pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
  timer: Prepare to change all DEFINE_TIMER() callbacks
  netfilter: ipvs: Convert timers to use timer_setup()
  scsi: qla2xxx: Convert timers to use timer_setup()
  block/aoe: discover_timer: Convert timers to use timer_setup()
  ide: Convert timers to use timer_setup()
  drbd: Convert timers to use timer_setup()
  mailbox: Convert timers to use timer_setup()
  crypto: Convert timers to use timer_setup()
  drivers/pcmcia: omap1: Fix error in automated timer conversion
  ARM: footbridge: Fix typo in timer conversion
  drivers/sgi-xp: Convert timers to use timer_setup()
  drivers/pcmcia: Convert timers to use timer_setup()
  drivers/memstick: Convert timers to use timer_setup()
  drivers/macintosh: Convert timers to use timer_setup()
  hwrng/xgene-rng: Convert timers to use timer_setup()
  auxdisplay: Convert timers to use timer_setup()
  sparc/led: Convert timers to use timer_setup()
  mips: ip22/32: Convert timers to use timer_setup()
  ...
2017-11-13 17:56:58 -08:00

1040 lines
26 KiB
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/math64.h>
#include "ntp_internal.h"
#include "timekeeping_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 time64_t 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 = (long)(__ktime_get_real_seconds() - time_reftime);
if (unlikely(time_status & STA_FREQHOLD))
secs = 0;
time_reftime = __ktime_get_real_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 = 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)
{
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 (time_state) {
case TIME_OK:
if (time_status & STA_INS) {
time_state = TIME_INS;
div_s64_rem(secs, SECS_PER_DAY, &rem);
ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
} else if (time_status & STA_DEL) {
time_state = TIME_DEL;
div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
}
break;
case TIME_INS:
if (!(time_status & STA_INS)) {
ntp_next_leap_sec = TIME64_MAX;
time_state = TIME_OK;
} else if (secs == ntp_next_leap_sec) {
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 == ntp_next_leap_sec) {
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;
}
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;
getnstimeofday64(&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;
getnstimeofday64(&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_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
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.
*/
getnstimeofday64(&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(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 = __ktime_get_real_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();
}
/*
* 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();
}