/* * linux/kernel/time/ntp.c * * NTP state machine interfaces and logic. * * This code was mainly moved from kernel/timer.c and kernel/time.c * Please see those files for relevant copyright info and historical * changelogs. */ #include <linux/mm.h> #include <linux/time.h> #include <linux/timex.h> #include <linux/jiffies.h> #include <linux/hrtimer.h> #include <linux/capability.h> #include <linux/math64.h> #include <linux/clocksource.h> #include <linux/workqueue.h> #include <asm/timex.h> /* * Timekeeping variables */ unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */ unsigned long tick_nsec; /* ACTHZ period (nsec) */ u64 tick_length; static u64 tick_length_base; static struct hrtimer leap_timer; #define MAX_TICKADJ 500 /* microsecs */ #define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \ NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) /* * phase-lock loop variables */ /* TIME_ERROR prevents overwriting the CMOS clock */ static int time_state = TIME_OK; /* clock synchronization status */ int time_status = STA_UNSYNC; /* clock status bits */ static long time_tai; /* TAI offset (s) */ static s64 time_offset; /* time adjustment (ns) */ static long time_constant = 2; /* pll time constant */ long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ static s64 time_freq; /* frequency offset (scaled ns/s)*/ static long time_reftime; /* time at last adjustment (s) */ long time_adjust; static long ntp_tick_adj; static void ntp_update_frequency(void) { u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT; second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT; second_length += time_freq; tick_length_base = second_length; tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ); } static void ntp_update_offset(long offset) { long mtemp; s64 freq_adj; if (!(time_status & STA_PLL)) return; if (!(time_status & STA_NANO)) offset *= NSEC_PER_USEC; /* * Scale the phase adjustment and * clamp to the operating range. */ offset = min(offset, MAXPHASE); offset = max(offset, -MAXPHASE); /* * Select how the frequency is to be controlled * and in which mode (PLL or FLL). */ if (time_status & STA_FREQHOLD || time_reftime == 0) time_reftime = xtime.tv_sec; mtemp = xtime.tv_sec - time_reftime; time_reftime = xtime.tv_sec; freq_adj = (s64)offset * mtemp; freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant); time_status &= ~STA_MODE; if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL), mtemp); time_status |= STA_MODE; } freq_adj += time_freq; freq_adj = min(freq_adj, MAXFREQ_SCALED); time_freq = max(freq_adj, -MAXFREQ_SCALED); time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); } /** * ntp_clear - Clears the NTP state variables * * Must be called while holding a write on the xtime_lock */ void ntp_clear(void) { time_adjust = 0; /* stop active adjtime() */ time_status |= STA_UNSYNC; time_maxerror = NTP_PHASE_LIMIT; time_esterror = NTP_PHASE_LIMIT; ntp_update_frequency(); tick_length = tick_length_base; time_offset = 0; } /* * 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. */ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) { enum hrtimer_restart res = HRTIMER_NORESTART; write_seqlock_irq(&xtime_lock); switch (time_state) { case TIME_OK: break; case TIME_INS: xtime.tv_sec--; wall_to_monotonic.tv_sec++; time_state = TIME_OOP; printk(KERN_NOTICE "Clock: " "inserting leap second 23:59:60 UTC\n"); hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC); res = HRTIMER_RESTART; break; case TIME_DEL: xtime.tv_sec++; time_tai--; wall_to_monotonic.tv_sec--; time_state = TIME_WAIT; printk(KERN_NOTICE "Clock: " "deleting leap second 23:59:59 UTC\n"); break; case TIME_OOP: time_tai++; time_state = TIME_WAIT; /* fall through */ case TIME_WAIT: if (!(time_status & (STA_INS | STA_DEL))) time_state = TIME_OK; break; } update_vsyscall(&xtime, clock); write_sequnlock_irq(&xtime_lock); return res; } /* * this routine handles the overflow of the microsecond field * * The tricky bits of code to handle the accurate clock support * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. * They were originally developed for SUN and DEC kernels. * All the kudos should go to Dave for this stuff. */ void second_overflow(void) { s64 time_adj; /* 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. The offset is * reduced by a fixed factor times the time constant. */ tick_length = tick_length_base; time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); time_offset -= time_adj; tick_length += time_adj; if (unlikely(time_adjust)) { if (time_adjust > MAX_TICKADJ) { time_adjust -= MAX_TICKADJ; tick_length += MAX_TICKADJ_SCALED; } else if (time_adjust < -MAX_TICKADJ) { time_adjust += MAX_TICKADJ; tick_length -= MAX_TICKADJ_SCALED; } else { tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT; time_adjust = 0; } } } #ifdef CONFIG_GENERIC_CMOS_UPDATE /* Disable the cmos update - used by virtualization and embedded */ int no_sync_cmos_clock __read_mostly; static void sync_cmos_clock(struct work_struct *work); static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); static void sync_cmos_clock(struct work_struct *work) { struct timespec now, next; int fail = 1; /* * If we have an externally synchronized Linux clock, then update * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be * called as close as possible to 500 ms before the new second starts. * This code is run on a timer. If the clock is set, that timer * may not expire at the correct time. Thus, we adjust... */ if (!ntp_synced()) /* * Not synced, exit, do not restart a timer (if one is * running, let it run out). */ return; getnstimeofday(&now); if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) fail = update_persistent_clock(now); next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); if (next.tv_nsec <= 0) next.tv_nsec += NSEC_PER_SEC; if (!fail) next.tv_sec = 659; else next.tv_sec = 0; if (next.tv_nsec >= NSEC_PER_SEC) { next.tv_sec++; next.tv_nsec -= NSEC_PER_SEC; } schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next)); } static void notify_cmos_timer(void) { if (!no_sync_cmos_clock) schedule_delayed_work(&sync_cmos_work, 0); } #else static inline void notify_cmos_timer(void) { } #endif /* adjtimex mainly allows reading (and writing, if superuser) of * kernel time-keeping variables. used by xntpd. */ int do_adjtimex(struct timex *txc) { struct timespec ts; int result; /* Validate the data before disabling interrupts */ 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% 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_STATUS && time_state != TIME_OK) hrtimer_cancel(&leap_timer); } getnstimeofday(&ts); write_seqlock_irq(&xtime_lock); /* If there are input parameters, then process them */ 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; goto adj_done; } if (txc->modes) { long sec; if (txc->modes & ADJ_STATUS) { if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { time_state = TIME_OK; time_status = STA_UNSYNC; } /* only set allowed bits */ time_status &= STA_RONLY; time_status |= txc->status & ~STA_RONLY; switch (time_state) { case TIME_OK: start_timer: sec = ts.tv_sec; if (time_status & STA_INS) { time_state = TIME_INS; sec += 86400 - sec % 86400; hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS); } else if (time_status & STA_DEL) { time_state = TIME_DEL; sec += 86400 - (sec + 1) % 86400; hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS); } break; case TIME_INS: case TIME_DEL: time_state = TIME_OK; goto start_timer; break; case TIME_WAIT: if (!(time_status & (STA_INS | STA_DEL))) time_state = TIME_OK; break; case TIME_OOP: hrtimer_restart(&leap_timer); break; } } 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 = (s64)txc->freq * PPM_SCALE; time_freq = min(time_freq, MAXFREQ_SCALED); time_freq = max(time_freq, -MAXFREQ_SCALED); } 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(); } txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT); if (!(time_status & STA_NANO)) txc->offset /= NSEC_PER_USEC; adj_done: result = time_state; /* mostly `TIME_OK' */ if (time_status & (STA_UNSYNC|STA_CLOCKERR)) result = TIME_ERROR; txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * (s64)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; /* PPS is not implemented, so these are zero */ txc->ppsfreq = 0; txc->jitter = 0; txc->shift = 0; txc->stabil = 0; txc->jitcnt = 0; txc->calcnt = 0; txc->errcnt = 0; txc->stbcnt = 0; write_sequnlock_irq(&xtime_lock); txc->time.tv_sec = ts.tv_sec; txc->time.tv_usec = ts.tv_nsec; if (!(time_status & STA_NANO)) txc->time.tv_usec /= NSEC_PER_USEC; notify_cmos_timer(); return result; } static int __init ntp_tick_adj_setup(char *str) { ntp_tick_adj = simple_strtol(str, NULL, 0); return 1; } __setup("ntp_tick_adj=", ntp_tick_adj_setup); void __init ntp_init(void) { ntp_clear(); hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS); leap_timer.function = ntp_leap_second; }