diff options
Diffstat (limited to 'sys/kern/kern_clock.c')
-rw-r--r-- | sys/kern/kern_clock.c | 707 |
1 files changed, 47 insertions, 660 deletions
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c index bd54b41..4d482e8 100644 --- a/sys/kern/kern_clock.c +++ b/sys/kern/kern_clock.c @@ -36,26 +36,9 @@ * SUCH DAMAGE. * * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 - * $Id: kern_clock.c,v 1.51 1998/01/11 00:44:27 phk Exp $ + * $Id: kern_clock.c,v 1.52 1998/01/11 19:07:58 phk Exp $ */ -/* Portions of this software are covered by the following: */ -/****************************************************************************** - * * - * Copyright (c) David L. Mills 1993, 1994 * - * * - * Permission to use, copy, modify, and distribute this software and its * - * documentation for any purpose and without fee is hereby granted, provided * - * that the above copyright notice appears in all copies and that both the * - * copyright notice and this permission notice appear in supporting * - * documentation, and that the name University of Delaware not be used in * - * advertising or publicity pertaining to distribution of the software * - * without specific, written prior permission. The University of Delaware * - * makes no representations about the suitability this software for any * - * purpose. It is provided "as is" without express or implied warranty. * - * * - *****************************************************************************/ - #include <sys/param.h> #include <sys/systm.h> #include <sys/dkstat.h> @@ -162,236 +145,6 @@ volatile struct timeval time; volatile struct timeval mono_time; /* - * Phase/frequency-lock loop (PLL/FLL) definitions - * - * The following variables are read and set by the ntp_adjtime() system - * call. - * - * time_state shows the state of the system clock, with values defined - * in the timex.h header file. - * - * time_status shows the status of the system clock, with bits defined - * in the timex.h header file. - * - * time_offset is used by the PLL/FLL to adjust the system time in small - * increments. - * - * time_constant determines the bandwidth or "stiffness" of the PLL. - * - * time_tolerance determines maximum frequency error or tolerance of the - * CPU clock oscillator and is a property of the architecture; however, - * in principle it could change as result of the presence of external - * discipline signals, for instance. - * - * time_precision is usually equal to the kernel tick variable; however, - * in cases where a precision clock counter or external clock is - * available, the resolution can be much less than this and depend on - * whether the external clock is working or not. - * - * time_maxerror is initialized by a ntp_adjtime() call and increased by - * the kernel once each second to reflect the maximum error - * bound growth. - * - * time_esterror is set and read by the ntp_adjtime() call, but - * otherwise not used by the kernel. - */ -int time_status = STA_UNSYNC; /* clock status bits */ -int time_state = TIME_OK; /* clock state */ -long time_offset = 0; /* time offset (us) */ -long time_constant = 0; /* pll time constant */ -long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */ -long time_precision = 1; /* clock precision (us) */ -long time_maxerror = MAXPHASE; /* maximum error (us) */ -long time_esterror = MAXPHASE; /* estimated error (us) */ - -/* - * The following variables establish the state of the PLL/FLL and the - * residual time and frequency offset of the local clock. The scale - * factors are defined in the timex.h header file. - * - * time_phase and time_freq are the phase increment and the frequency - * increment, respectively, of the kernel time variable at each tick of - * the clock. - * - * time_freq is set via ntp_adjtime() from a value stored in a file when - * the synchronization daemon is first started. Its value is retrieved - * via ntp_adjtime() and written to the file about once per hour by the - * daemon. - * - * time_adj is the adjustment added to the value of tick at each timer - * interrupt and is recomputed from time_phase and time_freq at each - * seconds rollover. - * - * time_reftime is the second's portion of the system time on the last - * call to ntp_adjtime(). It is used to adjust the time_freq variable - * and to increase the time_maxerror as the time since last update - * increases. - */ -static long time_phase = 0; /* phase offset (scaled us) */ -long time_freq = 0; /* frequency offset (scaled ppm) */ -static long time_adj = 0; /* tick adjust (scaled 1 / hz) */ -static long time_reftime = 0; /* time at last adjustment (s) */ - -#ifdef PPS_SYNC -/* - * The following variables are used only if the kernel PPS discipline - * code is configured (PPS_SYNC). The scale factors are defined in the - * timex.h header file. - * - * pps_time contains the time at each calibration interval, as read by - * microtime(). pps_count counts the seconds of the calibration - * interval, the duration of which is nominally pps_shift in powers of - * two. - * - * pps_offset is the time offset produced by the time median filter - * pps_tf[], while pps_jitter is the dispersion (jitter) measured by - * this filter. - * - * pps_freq is the frequency offset produced by the frequency median - * filter pps_ff[], while pps_stabil is the dispersion (wander) measured - * by this filter. - * - * pps_usec is latched from a high resolution counter or external clock - * at pps_time. Here we want the hardware counter contents only, not the - * contents plus the time_tv.usec as usual. - * - * pps_valid counts the number of seconds since the last PPS update. It - * is used as a watchdog timer to disable the PPS discipline should the - * PPS signal be lost. - * - * pps_glitch counts the number of seconds since the beginning of an - * offset burst more than tick/2 from current nominal offset. It is used - * mainly to suppress error bursts due to priority conflicts between the - * PPS interrupt and timer interrupt. - * - * pps_intcnt counts the calibration intervals for use in the interval- - * adaptation algorithm. It's just too complicated for words. - */ -struct timeval pps_time; /* kernel time at last interval */ -long pps_offset = 0; /* pps time offset (us) */ -long pps_jitter = MAXTIME; /* pps time dispersion (jitter) (us) */ -long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */ -long pps_freq = 0; /* frequency offset (scaled ppm) */ -long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */ -long pps_ff[] = {0, 0, 0}; /* frequency offset median filter */ -long pps_usec = 0; /* microsec counter at last interval */ -long pps_valid = PPS_VALID; /* pps signal watchdog counter */ -int pps_glitch = 0; /* pps signal glitch counter */ -int pps_count = 0; /* calibration interval counter (s) */ -int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */ -int pps_intcnt = 0; /* intervals at current duration */ - -/* - * PPS signal quality monitors - * - * pps_jitcnt counts the seconds that have been discarded because the - * jitter measured by the time median filter exceeds the limit MAXTIME - * (100 us). - * - * pps_calcnt counts the frequency calibration intervals, which are - * variable from 4 s to 256 s. - * - * pps_errcnt counts the calibration intervals which have been discarded - * because the wander exceeds the limit MAXFREQ (100 ppm) or where the - * calibration interval jitter exceeds two ticks. - * - * pps_stbcnt counts the calibration intervals that have been discarded - * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us). - */ -long pps_jitcnt = 0; /* jitter limit exceeded */ -long pps_calcnt = 0; /* calibration intervals */ -long pps_errcnt = 0; /* calibration errors */ -long pps_stbcnt = 0; /* stability limit exceeded */ -#endif /* PPS_SYNC */ - -/* XXX none of this stuff works under FreeBSD */ - -/* - * hardupdate() - local clock update - * - * This routine is called by ntp_adjtime() to update the local clock - * phase and frequency. The implementation is of an adaptive-parameter, - * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new - * time and frequency offset estimates for each call. If the kernel PPS - * discipline code is configured (PPS_SYNC), the PPS signal itself - * determines the new time offset, instead of the calling argument. - * Presumably, calls to ntp_adjtime() occur only when the caller - * believes the local clock is valid within some bound (+-128 ms with - * NTP). If the caller's time is far different than the PPS time, an - * argument will ensue, and it's not clear who will lose. - * - * For uncompensated quartz crystal oscillatores and nominal update - * intervals less than 1024 s, operation should be in phase-lock mode - * (STA_FLL = 0), where the loop is disciplined to phase. For update - * intervals greater than thiss, operation should be in frequency-lock - * mode (STA_FLL = 1), where the loop is disciplined to frequency. - * - * Note: splclock() is in effect. - */ -void -hardupdate(offset) - long offset; -{ - long ltemp, mtemp; - - if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME)) - return; - ltemp = offset; -#ifdef PPS_SYNC - if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) - ltemp = pps_offset; -#endif /* PPS_SYNC */ - - /* - * Scale the phase adjustment and clamp to the operating range. - */ - if (ltemp > MAXPHASE) - time_offset = MAXPHASE << SHIFT_UPDATE; - else if (ltemp < -MAXPHASE) - time_offset = -(MAXPHASE << SHIFT_UPDATE); - else - time_offset = ltemp << SHIFT_UPDATE; - - /* - * 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 = time.tv_sec; - mtemp = time.tv_sec - time_reftime; - time_reftime = time.tv_sec; - if (time_status & STA_FLL) { - if (mtemp >= MINSEC) { - ltemp = ((time_offset / mtemp) << (SHIFT_USEC - - SHIFT_UPDATE)); - if (ltemp < 0) - time_freq -= -ltemp >> SHIFT_KH; - else - time_freq += ltemp >> SHIFT_KH; - } - } else { - if (mtemp < MAXSEC) { - ltemp *= mtemp; - if (ltemp < 0) - time_freq -= -ltemp >> (time_constant + - time_constant + SHIFT_KF - - SHIFT_USEC); - else - time_freq += ltemp >> (time_constant + - time_constant + SHIFT_KF - - SHIFT_USEC); - } - } - if (time_freq > time_tolerance) - time_freq = time_tolerance; - else if (time_freq < -time_tolerance) - time_freq = -time_tolerance; -} - - - -/* * Initialize clock frequencies and start both clocks running. */ /* ARGSUSED*/ @@ -425,6 +178,9 @@ hardclock(frame) register struct clockframe *frame; { register struct proc *p; + int time_update; + struct timeval newtime = time; + long ltemp; p = curproc; if (p) { @@ -456,182 +212,54 @@ hardclock(frame) * Increment the time-of-day. */ ticks++; - { - int time_update; - struct timeval newtime = time; - long ltemp; - - if (timedelta == 0) { - time_update = CPU_THISTICKLEN(tick); - } else { - time_update = CPU_THISTICKLEN(tick) + tickdelta; - timedelta -= tickdelta; - } - BUMPTIME(&mono_time, time_update); - - /* - * Compute the phase adjustment. If the low-order bits - * (time_phase) of the update overflow, bump the high-order bits - * (time_update). - */ - time_phase += time_adj; - if (time_phase <= -FINEUSEC) { - ltemp = -time_phase >> SHIFT_SCALE; - time_phase += ltemp << SHIFT_SCALE; - time_update -= ltemp; - } - else if (time_phase >= FINEUSEC) { - ltemp = time_phase >> SHIFT_SCALE; - time_phase -= ltemp << SHIFT_SCALE; - time_update += ltemp; - } - - newtime.tv_usec += time_update; - /* - * On rollover of the second the phase adjustment to be used for - * the next second is calculated. Also, the maximum error is - * increased by the tolerance. If the PPS frequency discipline - * code is present, the phase is increased to compensate for the - * CPU clock oscillator frequency error. - * - * On a 32-bit machine and given parameters in the timex.h - * header file, the maximum phase adjustment is +-512 ms and - * maximum frequency offset is a tad less than) +-512 ppm. On a - * 64-bit machine, you shouldn't need to ask. - */ - if (newtime.tv_usec >= 1000000) { - newtime.tv_usec -= 1000000; - newtime.tv_sec++; - time_maxerror += time_tolerance >> SHIFT_USEC; - - /* - * 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. - */ - if (time_offset < 0) { - ltemp = -time_offset; - if (!(time_status & STA_FLL)) - ltemp >>= SHIFT_KG + time_constant; - if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) - ltemp = (MAXPHASE / MINSEC) << - SHIFT_UPDATE; - time_offset += ltemp; - time_adj = -ltemp << (SHIFT_SCALE - SHIFT_HZ - - SHIFT_UPDATE); - } else { - ltemp = time_offset; - if (!(time_status & STA_FLL)) - ltemp >>= SHIFT_KG + time_constant; - if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) - ltemp = (MAXPHASE / MINSEC) << - SHIFT_UPDATE; - time_offset -= ltemp; - time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - - SHIFT_UPDATE); - } - - /* - * Compute the frequency estimate and additional phase - * adjustment due to frequency error for the next - * second. When the PPS signal is engaged, gnaw on the - * watchdog counter and update the frequency computed by - * the pll and the PPS signal. - */ -#ifdef PPS_SYNC - pps_valid++; - if (pps_valid == PPS_VALID) { - pps_jitter = MAXTIME; - pps_stabil = MAXFREQ; - time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | - STA_PPSWANDER | STA_PPSERROR); - } - ltemp = time_freq + pps_freq; -#else - ltemp = time_freq; -#endif /* PPS_SYNC */ - if (ltemp < 0) - time_adj -= -ltemp >> - (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE); - else - time_adj += ltemp >> - (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE); - -#if SHIFT_HZ == 7 - /* - * When the CPU clock oscillator frequency is not a - * power of two in Hz, the SHIFT_HZ is only an - * approximate scale factor. In the SunOS kernel, this - * results in a PLL gain factor of 1/1.28 = 0.78 what it - * should be. In the following code the overall gain is - * increased by a factor of 1.25, which results in a - * residual error less than 3 percent. - */ - /* Same thing applies for FreeBSD --GAW */ - if (hz == 100) { - if (time_adj < 0) - time_adj -= -time_adj >> 2; - else - time_adj += time_adj >> 2; - } -#endif /* SHIFT_HZ */ - - /* XXX - this is really bogus, but can't be fixed until - xntpd's idea of the system clock is fixed to know how - the user wants leap seconds handled; in the mean time, - we assume that users of NTP are running without proper - leap second support (this is now the default anyway) */ - /* - * 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 (newtime.tv_sec % 86400 == 0) { - newtime.tv_sec--; - time_state = TIME_OOP; - } - break; - - case TIME_DEL: - if ((newtime.tv_sec + 1) % 86400 == 0) { - newtime.tv_sec++; - time_state = TIME_WAIT; - } - break; + if (timedelta == 0) { + time_update = CPU_THISTICKLEN(tick); + } else { + time_update = CPU_THISTICKLEN(tick) + tickdelta; + timedelta -= tickdelta; + } + BUMPTIME(&mono_time, time_update); - case TIME_OOP: - time_state = TIME_WAIT; - break; + /* + * Compute the phase adjustment. If the low-order bits + * (time_phase) of the update overflow, bump the high-order bits + * (time_update). + */ + time_phase += time_adj; + if (time_phase <= -FINEUSEC) { + ltemp = -time_phase >> SHIFT_SCALE; + time_phase += ltemp << SHIFT_SCALE; + time_update -= ltemp; + } + else if (time_phase >= FINEUSEC) { + ltemp = time_phase >> SHIFT_SCALE; + time_phase -= ltemp << SHIFT_SCALE; + time_update += ltemp; + } - case TIME_WAIT: - if (!(time_status & (STA_INS | STA_DEL))) - time_state = TIME_OK; - } - } - CPU_CLOCKUPDATE(&time, &newtime); + newtime.tv_usec += time_update; + /* + * On rollover of the second the phase adjustment to be used for + * the next second is calculated. Also, the maximum error is + * increased by the tolerance. If the PPS frequency discipline + * code is present, the phase is increased to compensate for the + * CPU clock oscillator frequency error. + * + * On a 32-bit machine and given parameters in the timex.h + * header file, the maximum phase adjustment is +-512 ms and + * maximum frequency offset is a tad less than) +-512 ppm. On a + * 64-bit machine, you shouldn't need to ask. + */ + if (newtime.tv_usec >= 1000000) { + newtime.tv_usec -= 1000000; + newtime.tv_sec++; + ntp_update_second(&newtime.tv_sec); } - - if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) { + CPU_CLOCKUPDATE(&time, &newtime); + + if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) setsoftclock(); - } } void @@ -900,244 +528,3 @@ sysctl_kern_clockrate SYSCTL_HANDLER_ARGS SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD, 0, 0, sysctl_kern_clockrate, "S,clockinfo",""); -#ifdef PPS_SYNC - -/* We need this ugly monster twice, so lets macroize it... */ - -#define MEDIAN3(a, m, s) \ - do { \ - if (a[0] > a[1]) { \ - if (a[1] > a[2]) { \ - /* 0 1 2 */ \ - m = a[1]; \ - s = a[0] - a[2]; \ - } else if (a[2] > a[0]) { \ - /* 2 0 1 */ \ - m = a[0]; \ - s = a[2] - a[1]; \ - } else { \ - /* 0 2 1 */ \ - m = a[2]; \ - s = a[0] - a[1]; \ - } \ - } else { \ - if (a[1] < a[2]) { \ - /* 2 1 0 */ \ - m = a[1]; \ - s = a[2] - a[0]; \ - } else if (a[2] < a[0]) { \ - /* 1 0 2 */ \ - m = a[0]; \ - s = a[1] - a[2]; \ - } else { \ - /* 1 2 0 */ \ - m = a[2]; \ - s = a[1] - a[0]; \ - } \ - } \ - } while (0) - -/* - * hardpps() - discipline CPU clock oscillator to external PPS signal - * - * This routine is called at each PPS interrupt in order to discipline - * the CPU clock oscillator to the PPS signal. It measures the PPS phase - * and leaves it in a handy spot for the hardclock() routine. It - * integrates successive PPS phase differences and calculates the - * frequency offset. This is used in hardclock() to discipline the CPU - * clock oscillator so that intrinsic frequency error is cancelled out. - * The code requires the caller to capture the time and hardware counter - * value at the on-time PPS signal transition. - * - * Note that, on some Unix systems, this routine runs at an interrupt - * priority level higher than the timer interrupt routine hardclock(). - * Therefore, the variables used are distinct from the hardclock() - * variables, except for certain exceptions: The PPS frequency pps_freq - * and phase pps_offset variables are determined by this routine and - * updated atomically. The time_tolerance variable can be considered a - * constant, since it is infrequently changed, and then only when the - * PPS signal is disabled. The watchdog counter pps_valid is updated - * once per second by hardclock() and is atomically cleared in this - * routine. - */ -void -hardpps(tvp, p_usec) - struct timeval *tvp; /* time at PPS */ - long p_usec; /* hardware counter at PPS */ -{ - long u_usec, v_usec, bigtick; - long cal_sec, cal_usec; - - /* - * An occasional glitch can be produced when the PPS interrupt - * occurs in the hardclock() routine before the time variable is - * updated. Here the offset is discarded when the difference - * between it and the last one is greater than tick/2, but not - * if the interval since the first discard exceeds 30 s. - */ - time_status |= STA_PPSSIGNAL; - time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); - pps_valid = 0; - u_usec = -tvp->tv_usec; - if (u_usec < -500000) - u_usec += 1000000; - v_usec = pps_offset - u_usec; - if (v_usec < 0) - v_usec = -v_usec; - if (v_usec > (tick >> 1)) { - if (pps_glitch > MAXGLITCH) { - pps_glitch = 0; - pps_tf[2] = u_usec; - pps_tf[1] = u_usec; - } else { - pps_glitch++; - u_usec = pps_offset; - } - } else - pps_glitch = 0; - - /* - * A three-stage median filter is used to help deglitch the pps - * time. The median sample becomes the time offset estimate; the - * difference between the other two samples becomes the time - * dispersion (jitter) estimate. - */ - pps_tf[2] = pps_tf[1]; - pps_tf[1] = pps_tf[0]; - pps_tf[0] = u_usec; - - MEDIAN3(pps_tf, pps_offset, v_usec); - - if (v_usec > MAXTIME) - pps_jitcnt++; - v_usec = (v_usec << PPS_AVG) - pps_jitter; - if (v_usec < 0) - pps_jitter -= -v_usec >> PPS_AVG; - else - pps_jitter += v_usec >> PPS_AVG; - if (pps_jitter > (MAXTIME >> 1)) - time_status |= STA_PPSJITTER; - - /* - * During the calibration interval adjust the starting time when - * the tick overflows. At the end of the interval compute the - * duration of the interval and the difference of the hardware - * counters at the beginning and end of the interval. This code - * is deliciously complicated by the fact valid differences may - * exceed the value of tick when using long calibration - * intervals and small ticks. Note that the counter can be - * greater than tick if caught at just the wrong instant, but - * the values returned and used here are correct. - */ - bigtick = (long)tick << SHIFT_USEC; - pps_usec -= pps_freq; - if (pps_usec >= bigtick) - pps_usec -= bigtick; - if (pps_usec < 0) - pps_usec += bigtick; - pps_time.tv_sec++; - pps_count++; - if (pps_count < (1 << pps_shift)) - return; - pps_count = 0; - pps_calcnt++; - u_usec = p_usec << SHIFT_USEC; - v_usec = pps_usec - u_usec; - if (v_usec >= bigtick >> 1) - v_usec -= bigtick; - if (v_usec < -(bigtick >> 1)) - v_usec += bigtick; - if (v_usec < 0) - v_usec = -(-v_usec >> pps_shift); - else - v_usec = v_usec >> pps_shift; - pps_usec = u_usec; - cal_sec = tvp->tv_sec; - cal_usec = tvp->tv_usec; - cal_sec -= pps_time.tv_sec; - cal_usec -= pps_time.tv_usec; - if (cal_usec < 0) { - cal_usec += 1000000; - cal_sec--; - } - pps_time = *tvp; - - /* - * Check for lost interrupts, noise, excessive jitter and - * excessive frequency error. The number of timer ticks during - * the interval may vary +-1 tick. Add to this a margin of one - * tick for the PPS signal jitter and maximum frequency - * deviation. If the limits are exceeded, the calibration - * interval is reset to the minimum and we start over. - */ - u_usec = (long)tick << 1; - if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec)) - || (cal_sec == 0 && cal_usec < u_usec)) - || v_usec > time_tolerance || v_usec < -time_tolerance) { - pps_errcnt++; - pps_shift = PPS_SHIFT; - pps_intcnt = 0; - time_status |= STA_PPSERROR; - return; - } - - /* - * A three-stage median filter is used to help deglitch the pps - * frequency. The median sample becomes the frequency offset - * estimate; the difference between the other two samples - * becomes the frequency dispersion (stability) estimate. - */ - pps_ff[2] = pps_ff[1]; - pps_ff[1] = pps_ff[0]; - pps_ff[0] = v_usec; - - MEDIAN3(pps_ff, u_usec, v_usec); - - /* - * Here the frequency dispersion (stability) is updated. If it - * is less than one-fourth the maximum (MAXFREQ), the frequency - * offset is updated as well, but clamped to the tolerance. It - * will be processed later by the hardclock() routine. - */ - v_usec = (v_usec >> 1) - pps_stabil; - if (v_usec < 0) - pps_stabil -= -v_usec >> PPS_AVG; - else - pps_stabil += v_usec >> PPS_AVG; - if (pps_stabil > MAXFREQ >> 2) { - pps_stbcnt++; - time_status |= STA_PPSWANDER; - return; - } - if (time_status & STA_PPSFREQ) { - if (u_usec < 0) { - pps_freq -= -u_usec >> PPS_AVG; - if (pps_freq < -time_tolerance) - pps_freq = -time_tolerance; - u_usec = -u_usec; - } else { - pps_freq += u_usec >> PPS_AVG; - if (pps_freq > time_tolerance) - pps_freq = time_tolerance; - } - } - - /* - * Here the calibration interval is adjusted. If the maximum - * time difference is greater than tick / 4, reduce the interval - * by half. If this is not the case for four consecutive - * intervals, double the interval. - */ - if (u_usec << pps_shift > bigtick >> 2) { - pps_intcnt = 0; - if (pps_shift > PPS_SHIFT) - pps_shift--; - } else if (pps_intcnt >= 4) { - pps_intcnt = 0; - if (pps_shift < PPS_SHIFTMAX) - pps_shift++; - } else - pps_intcnt++; -} -#endif /* PPS_SYNC */ - |