X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/d2ca7c1139e9724bef21ce7cae03cc419229b898..c01ca9709f7728353e608a09b815a10dc93eaa73:/sys/kern/kern_clock.c diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c index fc90d25e7a..a336f75840 100644 --- a/sys/kern/kern_clock.c +++ b/sys/kern/kern_clock.c @@ -31,16 +31,36 @@ * SUCH DAMAGE. * * from: @(#)kern_clock.c 7.16 (Berkeley) 5/9/91 - * $Id: kern_clock.c,v 1.3 1993/10/19 01:05:36 nate Exp $ + * $Id: kern_clock.c,v 1.15 1994/04/02 08:39:20 davidg 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 "param.h" #include "systm.h" #include "dkstat.h" #include "callout.h" #include "kernel.h" #include "proc.h" +#include "signalvar.h" #include "resourcevar.h" +#include "timex.h" #include "machine/cpu.h" @@ -51,6 +71,12 @@ #include "gprof.h" #endif +static void gatherstats(clockframe *); + +/* From callout.h */ +struct callout *callfree, *callout, calltodo; +int ncallout; + /* * Clock handling routines. * @@ -85,24 +111,258 @@ } \ } +/* + * Phase-lock loop (PLL) 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 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 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 at each timer interrupt. + * + * 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. + */ +long time_phase = 0; /* phase offset (scaled us) */ +long time_freq = 0; /* frequency offset (scaled ppm) */ +long time_adj = 0; /* tick adjust (scaled 1 / hz) */ +long time_reftime = 0; /* time at last adjustment (s) */ + +#ifdef PPS_SYNC +/* + * The following variables are used only if the 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_offset is the time offset produced by the time median filter + * pps_tf[], while pps_jitter is the dispersion measured by this + * filter. + * + * pps_freq is the frequency offset produced by the frequency median + * filter pps_ff[], while pps_stabil is the dispersion 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_count counts the seconds of the calibration interval, the + * duration of which is pps_shift in powers of two. + * + * 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 */ +#ifdef EXT_CLOCK +/* + * External clock definitions + * + * The following definitions and declarations are used only if an + * external clock (HIGHBALL or TPRO) is configured on the system. + */ +#define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */ + +/* + * The clock_count variable is set to CLOCK_INTERVAL at each PPS + * interrupt and decremented once each second. + */ +int clock_count = 0; /* CPU clock counter */ + +#ifdef HIGHBALL +/* + * The clock_offset and clock_cpu variables are used by the HIGHBALL + * interface. The clock_offset variable defines the offset between + * system time and the HIGBALL counters. The clock_cpu variable contains + * the offset between the system clock and the HIGHBALL clock for use in + * disciplining the kernel time variable. + */ +extern struct timeval clock_offset; /* Highball clock offset */ +long clock_cpu = 0; /* CPU clock adjust */ +#endif /* HIGHBALL */ +#endif /* EXT_CLOCK */ + +/* + * hardupdate() - local clock update + * + * This routine is called by ntp_adjtime() to update the local clock + * phase and frequency. This is used to implement an adaptive-parameter, + * first-order, type-II phase-lock loop. The code computes new time and + * frequency offsets each time it is called. The hardclock() routine + * amortizes these offsets at each tick interrupt. 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 default SHIFT_UPDATE = 12, the offset is limited to +-512 ms, the + * maximum interval between updates is 4096 s and the maximum frequency + * offset is +-31.25 ms/s. + * + * 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 */ + if (ltemp > MAXPHASE) + time_offset = MAXPHASE << SHIFT_UPDATE; + else if (ltemp < -MAXPHASE) + time_offset = -(MAXPHASE << SHIFT_UPDATE); + else + time_offset = ltemp << SHIFT_UPDATE; + mtemp = time.tv_sec - time_reftime; + time_reftime = time.tv_sec; + if (mtemp > MAXSEC) + mtemp = 0; + + /* ugly multiply should be replaced */ + if (ltemp < 0) + time_freq -= (-ltemp * mtemp) >> (time_constant + + time_constant + SHIFT_KF - SHIFT_USEC); + else + time_freq += (ltemp * mtemp) >> (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; +} + + + /* * The hz hardware interval timer. * We update the events relating to real time. * If this timer is also being used to gather statistics, * we run through the statistics gathering routine as well. */ +void hardclock(frame) clockframe frame; { register struct callout *p1; register struct proc *p = curproc; - register struct pstats *pstats; + register struct pstats *pstats = 0; register struct rusage *ru; register struct vmspace *vm; register int s; int needsoft = 0; extern int tickdelta; extern long timedelta; + long ltemp, time_update = 0; /* * Update real-time timeout queue. @@ -226,49 +486,164 @@ hardclock(frame) * so we don't keep the relatively high clock interrupt * priority any longer than necessary. */ - if (timedelta == 0) - BUMPTIME(&time, tick) - else { - register delta; - - if (timedelta < 0) { - delta = tick - tickdelta; - timedelta += tickdelta; + { + int time_update; + if (timedelta == 0) { + time_update = tick; } else { - delta = tick + tickdelta; - timedelta -= tickdelta; + if (timedelta < 0) { + time_update = tick - tickdelta; + timedelta += tickdelta; + } else { + time_update = tick + tickdelta; + timedelta -= tickdelta; + } + } + /* + * 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; + } + + time.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. + * + * With SHIFT_SCALE = 23, the maximum frequency adjustment is + * +-256 us per tick, or 25.6 ms/s at a clock frequency of 100 + * Hz. The time contribution is shifted right a minimum of two + * bits, while the frequency contribution is a right shift. + * Thus, overflow is prevented if the frequency contribution is + * limited to half the maximum or 15.625 ms/s. + */ + if (time.tv_usec >= 1000000) { + time.tv_usec -= 1000000; + time.tv_sec++; + time_maxerror += time_tolerance >> SHIFT_USEC; + if (time_offset < 0) { + ltemp = -time_offset >> + (SHIFT_KG + time_constant); + time_offset += ltemp; + time_adj = -ltemp << + (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE); + } else { + ltemp = time_offset >> + (SHIFT_KG + time_constant); + time_offset -= ltemp; + time_adj = ltemp << + (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE); + } +#ifdef PPS_SYNC + /* + * Gnaw on the watchdog counter and update the frequency + * computed by the pll and the PPS signal. + */ + 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); + + /* + * 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; + } + + /* 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 (time.tv_sec % 86400 == 0) { + time.tv_sec--; + time_state = TIME_OOP; + } + break; + + case TIME_DEL: + if ((time.tv_sec + 1) % 86400 == 0) { + time.tv_sec++; + time_state = TIME_WAIT; + } + break; + + case TIME_OOP: + time_state = TIME_WAIT; + break; + + case TIME_WAIT: + if (!(time_status & (STA_INS | STA_DEL))) + time_state = TIME_OK; + } } - BUMPTIME(&time, delta); } -#ifdef DCFCLK - /* - * This is lousy, but until I can get the $&^%&^(!!! signal onto one - * of the interrupt's I'll have to poll it. No, it will not work if - * you attempt -DHZ=1000, things break. - * But keep the NDCFCLK low, to avoid waste of cycles... - * phk@data.fls.dk - */ - dcfclk_worker(); -#endif if (needsoft) { -#if 0 -/* - * XXX - hardclock runs at splhigh, so the splsoftclock is useless and - * softclock runs at splhigh as well if we do this. It is not much of - * an optimization, since the "software interrupt" is done with a call - * from doreti, and the overhead of checking there is sometimes less - * than checking here. Moreover, the whole %$$%$^ frame is passed by - * value here. - */ if (CLKF_BASEPRI(&frame)) { /* * Save the overhead of a software interrupt; * it will happen as soon as we return, so do it now. */ (void) splsoftclock(); - softclock(frame); + softclock(CLKF_USERMODE(&frame)); } else -#endif setsoftclock(); } } @@ -282,6 +657,7 @@ int dk_ndrive = DK_NDRIVE; * or idle state) for the entire last time interval, and * update statistics accordingly. */ +void gatherstats(framep) clockframe *framep; { @@ -313,7 +689,7 @@ gatherstats(framep) cpstate = CP_SYS; if (curproc == NULL && CLKF_BASEPRI(framep)) cpstate = CP_IDLE; -#ifdef GPROF +#if defined(GPROF) && !defined(GUPROF) s = (u_long) CLKF_PC(framep) - (u_long) s_lowpc; if (profiling < 2 && s < s_textsize) kcount[s / (HISTFRACTION * sizeof (*kcount))]++; @@ -334,15 +710,15 @@ gatherstats(framep) * Software priority level clock interrupt. * Run periodic events from timeout queue. */ -/*ARGSUSED*/ -softclock(frame) - clockframe frame; +void +softclock(usermode) + int usermode; { for (;;) { register struct callout *p1; register caddr_t arg; - register int (*func)(); + register timeout_func_t func; register int a, s; s = splhigh(); @@ -367,11 +743,11 @@ softclock(frame) * If trapped user-mode and profiling, give it * a profiling tick. */ - if (CLKF_USERMODE(&frame)) { + if (usermode) { register struct proc *p = curproc; if (p->p_stats->p_prof.pr_scale) - profile_tick(p, &frame); + profile_tick(p, unused was &frame); /* * Check to see if process has accumulated * more than 10 minutes of user time. If so @@ -389,8 +765,9 @@ softclock(frame) /* * Arrange that (*func)(arg) is called in t/hz seconds. */ +void timeout(func, arg, t) - int (*func)(); + timeout_func_t func; caddr_t arg; register int t; { @@ -420,8 +797,9 @@ timeout(func, arg, t) * untimeout is called to remove a function timeout call * from the callout structure. */ +void untimeout(func, arg) - int (*func)(); + timeout_func_t func; caddr_t arg; { register struct callout *p1, *p2; @@ -446,30 +824,224 @@ untimeout(func, arg) * Used to compute third argument to timeout() from an * absolute time. */ + +/* XXX clock_t */ +u_long hzto(tv) struct timeval *tv; { - register long ticks; + register unsigned long ticks; register long sec; - int s = splhigh(); + register long usec; + int s; /* - * If number of milliseconds will fit in 32 bit arithmetic, - * then compute number of milliseconds to time and scale to - * ticks. Otherwise just compute number of hz in time, rounding - * times greater than representible to maximum value. + * If the number of usecs in the whole seconds part of the time + * difference fits in a long, then the total number of usecs will + * fit in an unsigned long. Compute the total and convert it to + * ticks, rounding up and adding 1 to allow for the current tick + * to expire. Rounding also depends on unsigned long arithmetic + * to avoid overflow. + * + * Otherwise, if the number of ticks in the whole seconds part of + * the time difference fits in a long, then convert the parts to + * ticks separately and add, using similar rounding methods and + * overflow avoidance. This method would work in the previous + * case but it is slightly slower and assumes that hz is integral. * - * Delta times less than 25 days can be computed ``exactly''. - * Maximum value for any timeout in 10ms ticks is 250 days. + * Otherwise, round the time difference down to the maximum + * representable value. + * + * Maximum value for any timeout in 10ms ticks is 248 days. */ + s = splhigh(); sec = tv->tv_sec - time.tv_sec; - if (sec <= 0x7fffffff / 1000 - 1000) - ticks = ((tv->tv_sec - time.tv_sec) * 1000 + - (tv->tv_usec - time.tv_usec) / 1000) / (tick / 1000); - else if (sec <= 0x7fffffff / hz) - ticks = sec * hz; - else - ticks = 0x7fffffff; + usec = tv->tv_usec - time.tv_usec; splx(s); + if (usec < 0) { + sec--; + usec += 1000000; + } + if (sec < 0) { +#ifdef DIAGNOSTIC + printf("hzto: negative time difference %ld sec %ld usec\n", + sec, usec); +#endif + ticks = 1; + } else if (sec <= LONG_MAX / 1000000) + ticks = (sec * 1000000 + (unsigned long)usec + (tick - 1)) + / tick + 1; + else if (sec <= LONG_MAX / hz) + ticks = sec * hz + + ((unsigned long)usec + (tick - 1)) / tick + 1; + else + ticks = LONG_MAX; +#define CLOCK_T_MAX INT_MAX /* XXX should be ULONG_MAX */ + if (ticks > CLOCK_T_MAX) + ticks = CLOCK_T_MAX; return (ticks); } + +#ifdef PPS_SYNC +/* + * 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 integrates successive + * phase differences between the two oscillators 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 designated PPS signal transition. + */ +void +hardpps(tvp, usec) + struct timeval *tvp; /* time at PPS */ + long usec; /* hardware counter at PPS */ +{ + long u_usec, v_usec, bigtick; + long cal_sec, cal_usec; + + /* + * 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 -= ntp_pll.ybar; + 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; + ntp_pll.calcnt++; + u_usec = 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 >> ntp_pll.shift); + else + v_usec = v_usec >> ntp_pll.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 > ntp_pll.tolerance || v_usec < -ntp_pll.tolerance) { + ntp_pll.jitcnt++; + ntp_pll.shift = NTP_PLL.SHIFT; + pps_dispinc = PPS_DISPINC; + ntp_pll.intcnt = 0; + return; + } + + /* + * A three-stage median filter is used to help deglitch the pps + * signal. The median sample becomes the offset estimate; the + * difference between the other two samples becomes the + * dispersion estimate. + */ + pps_mf[2] = pps_mf[1]; + pps_mf[1] = pps_mf[0]; + pps_mf[0] = v_usec; + if (pps_mf[0] > pps_mf[1]) { + if (pps_mf[1] > pps_mf[2]) { + u_usec = pps_mf[1]; /* 0 1 2 */ + v_usec = pps_mf[0] - pps_mf[2]; + } else if (pps_mf[2] > pps_mf[0]) { + u_usec = pps_mf[0]; /* 2 0 1 */ + v_usec = pps_mf[2] - pps_mf[1]; + } else { + u_usec = pps_mf[2]; /* 0 2 1 */ + v_usec = pps_mf[0] - pps_mf[1]; + } + } else { + if (pps_mf[1] < pps_mf[2]) { + u_usec = pps_mf[1]; /* 2 1 0 */ + v_usec = pps_mf[2] - pps_mf[0]; + } else if (pps_mf[2] < pps_mf[0]) { + u_usec = pps_mf[0]; /* 1 0 2 */ + v_usec = pps_mf[1] - pps_mf[2]; + } else { + u_usec = pps_mf[2]; /* 1 2 0 */ + v_usec = pps_mf[1] - pps_mf[0]; + } + } + + /* + * Here the dispersion average is updated. If it is less than + * the threshold pps_dispmax, the frequency average is updated + * as well, but clamped to the tolerance. + */ + v_usec = (v_usec >> 1) - ntp_pll.disp; + if (v_usec < 0) + ntp_pll.disp -= -v_usec >> PPS_AVG; + else + ntp_pll.disp += v_usec >> PPS_AVG; + if (ntp_pll.disp > pps_dispmax) { + ntp_pll.discnt++; + return; + } + if (u_usec < 0) { + ntp_pll.ybar -= -u_usec >> PPS_AVG; + if (ntp_pll.ybar < -ntp_pll.tolerance) + ntp_pll.ybar = -ntp_pll.tolerance; + u_usec = -u_usec; + } else { + ntp_pll.ybar += u_usec >> PPS_AVG; + if (ntp_pll.ybar > ntp_pll.tolerance) + ntp_pll.ybar = ntp_pll.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 << ntp_pll.shift > bigtick >> 2) { + ntp_pll.intcnt = 0; + if (ntp_pll.shift > NTP_PLL.SHIFT) { + ntp_pll.shift--; + pps_dispinc <<= 1; + } + } else if (ntp_pll.intcnt >= 4) { + ntp_pll.intcnt = 0; + if (ntp_pll.shift < NTP_PLL.SHIFTMAX) { + ntp_pll.shift++; + pps_dispinc >>= 1; + } + } else + ntp_pll.intcnt++; +} +#endif /* PPS_SYNC */