/* * 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 <asm/div64.h> #include <asm/timex.h> /* * Timekeeping variables */ unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */ unsigned long tick_nsec; /* ACTHZ period (nsec) */ static u64 tick_length, tick_length_base; #define MAX_TICKADJ 500 /* microsecs */ #define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \ TICK_LENGTH_SHIFT) / HZ) /* * phase-lock loop variables */ /* TIME_ERROR prevents overwriting the CMOS clock */ int time_state = TIME_OK; /* clock synchronization status */ int time_status = STA_UNSYNC; /* clock status bits */ long time_offset; /* time adjustment (ns) */ long time_constant = 2; /* pll time constant */ long time_precision = 1; /* clock precision (us) */ long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ long time_freq; /* frequency offset (scaled ppm)*/ long time_reftime; /* time at last adjustment (s) */ long time_adjust; /** * 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; } #define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE) #define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE) void ntp_update_frequency(void) { tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT; tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT; tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC); do_div(tick_length_base, HZ); tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT; } /* * 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) { long time_adj; /* Bump the maxerror field */ time_maxerror += MAXFREQ >> SHIFT_USEC; if (time_maxerror > NTP_PHASE_LIMIT) { time_maxerror = NTP_PHASE_LIMIT; time_status |= STA_UNSYNC; } /* * 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. The microtime() * routine or external clock driver will insure that reported time is * always monotonic. The ugly divides should be replaced. */ switch (time_state) { case TIME_OK: if (time_status & STA_INS) time_state = TIME_INS; else if (time_status & STA_DEL) time_state = TIME_DEL; break; case TIME_INS: if (xtime.tv_sec % 86400 == 0) { xtime.tv_sec--; wall_to_monotonic.tv_sec++; /* * The timer interpolator will make time change * gradually instead of an immediate jump by one second */ time_interpolator_update(-NSEC_PER_SEC); time_state = TIME_OOP; clock_was_set(); printk(KERN_NOTICE "Clock: inserting leap second " "23:59:60 UTC\n"); } break; case TIME_DEL: if ((xtime.tv_sec + 1) % 86400 == 0) { xtime.tv_sec++; wall_to_monotonic.tv_sec--; /* * Use of time interpolator for a gradual change of * time */ time_interpolator_update(NSEC_PER_SEC); time_state = TIME_WAIT; clock_was_set(); printk(KERN_NOTICE "Clock: deleting leap second " "23:59:59 UTC\n"); } break; case TIME_OOP: time_state = TIME_WAIT; break; case TIME_WAIT: if (!(time_status & (STA_INS | STA_DEL))) time_state = TIME_OK; } /* * Compute the phase adjustment for the next second. In PLL mode, the * offset is reduced by a fixed factor times the time constant. In FLL * mode the offset is used directly. In either mode, the maximum phase * adjustment for each second is clamped so as to spread the adjustment * over not more than the number of seconds between updates. */ tick_length = tick_length_base; time_adj = time_offset; if (!(time_status & STA_FLL)) time_adj = shift_right(time_adj, SHIFT_KG + time_constant); time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC); time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC); time_offset -= time_adj; tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); 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 { time_adjust = 0; tick_length += (s64)(time_adjust * NSEC_PER_USEC / HZ) << TICK_LENGTH_SHIFT; } } } /* * Return how long ticks are at the moment, that is, how much time * update_wall_time_one_tick will add to xtime next time we call it * (assuming no calls to do_adjtimex in the meantime). * The return value is in fixed-point nanoseconds shifted by the * specified number of bits to the right of the binary point. * This function has no side-effects. */ u64 current_tick_length(void) { return tick_length; } void __attribute__ ((weak)) notify_arch_cmos_timer(void) { return; } /* adjtimex mainly allows reading (and writing, if superuser) of * kernel time-keeping variables. used by xntpd. */ int do_adjtimex(struct timex *txc) { long ltemp, mtemp, save_adjust; s64 freq_adj; int result; /* In order to modify anything, you gotta be super-user! */ if (txc->modes && !capable(CAP_SYS_TIME)) return -EPERM; /* Now we validate the data before disabling interrupts */ if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) /* singleshot must not be used with any other mode bits */ if (txc->modes != ADJ_OFFSET_SINGLESHOT) return -EINVAL; if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET)) /* adjustment Offset limited to +- .512 seconds */ if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE ) return -EINVAL; /* if the quartz is off by more than 10% something is VERY wrong ! */ if (txc->modes & ADJ_TICK) if (txc->tick < 900000/USER_HZ || txc->tick > 1100000/USER_HZ) return -EINVAL; write_seqlock_irq(&xtime_lock); result = time_state; /* mostly `TIME_OK' */ /* Save for later - semantics of adjtime is to return old value */ save_adjust = time_adjust; #if 0 /* STA_CLOCKERR is never set yet */ time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */ #endif /* If there are input parameters, then process them */ if (txc->modes) { if (txc->modes & ADJ_STATUS) /* only set allowed bits */ time_status = (txc->status & ~STA_RONLY) | (time_status & STA_RONLY); if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */ if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) { result = -EINVAL; goto leave; } time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC); } if (txc->modes & ADJ_MAXERROR) { if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) { result = -EINVAL; goto leave; } time_maxerror = txc->maxerror; } if (txc->modes & ADJ_ESTERROR) { if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) { result = -EINVAL; goto leave; } time_esterror = txc->esterror; } if (txc->modes & ADJ_TIMECONST) { /* p. 24 */ if (txc->constant < 0) { /* NTP v4 uses values > 6 */ result = -EINVAL; goto leave; } time_constant = txc->constant; } if (txc->modes & ADJ_OFFSET) { /* values checked earlier */ if (txc->modes == ADJ_OFFSET_SINGLESHOT) { /* adjtime() is independent from ntp_adjtime() */ time_adjust = txc->offset; } else if (time_status & STA_PLL) { ltemp = txc->offset * NSEC_PER_USEC; /* * Scale the phase adjustment and * clamp to the operating range. */ time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC); time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC); /* * Select whether the frequency is to be controlled * and in which mode (PLL or FLL). Clamp to the operating * range. Ugly multiply/divide should be replaced someday. */ 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 = 0; if (time_status & STA_FLL) { if (mtemp >= MINSEC) { freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH); if (time_offset < 0) { freq_adj = -freq_adj; do_div(freq_adj, mtemp); freq_adj = -freq_adj; } else do_div(freq_adj, mtemp); } else /* calibration interval too short (p. 12) */ result = TIME_ERROR; } else { /* PLL mode */ if (mtemp < MAXSEC) { freq_adj = (s64)ltemp * mtemp; freq_adj = shift_right(freq_adj,(time_constant + time_constant + SHIFT_KF - SHIFT_NSEC)); } else /* calibration interval too long (p. 12) */ result = TIME_ERROR; } freq_adj += time_freq; freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC); time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC); time_offset = (time_offset / HZ) << SHIFT_UPDATE; } /* STA_PLL */ } /* txc->modes & ADJ_OFFSET */ if (txc->modes & ADJ_TICK) tick_usec = txc->tick; if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) ntp_update_frequency(); } /* txc->modes */ leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) result = TIME_ERROR; if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) txc->offset = save_adjust; else txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000; txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC); txc->maxerror = time_maxerror; txc->esterror = time_esterror; txc->status = time_status; txc->constant = time_constant; txc->precision = time_precision; txc->tolerance = MAXFREQ; txc->tick = tick_usec; /* 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); do_gettimeofday(&txc->time); notify_arch_cmos_timer(); return(result); }