diff options
Diffstat (limited to 'sys/kern/kern_clock.c')
| -rw-r--r-- | sys/kern/kern_clock.c | 441 |
1 files changed, 396 insertions, 45 deletions
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c index 86592699658..2251d744e26 100644 --- a/sys/kern/kern_clock.c +++ b/sys/kern/kern_clock.c @@ -1,4 +1,4 @@ -/* $NetBSD: kern_clock.c,v 1.24 1996/01/17 04:37:31 cgd Exp $ */ +/* $NetBSD: kern_clock.c,v 1.23 1995/12/28 19:16:41 thorpej Exp $ */ /*- * Copyright (c) 1982, 1986, 1991, 1993 @@ -40,6 +40,23 @@ * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 */ +/* 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> @@ -47,6 +64,7 @@ #include <sys/kernel.h> #include <sys/proc.h> #include <sys/resourcevar.h> +#include <sys/timex.h> #include <machine/cpu.h> @@ -103,13 +121,212 @@ int profprocs; int ticks; static int psdiv, pscnt; /* prof => stat divider */ int psratio; /* ratio: prof / stat */ -int tickfix, tickfixinterval; /* used if tick not really integral */ -static int tickfixcnt; /* number of ticks since last fix */ volatile struct timeval time; volatile struct timeval mono_time; /* + * 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. + */ +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 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 */ + +/* + * 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; +} + +/* * Initialize clock frequencies and start both clocks running. */ void @@ -142,9 +359,10 @@ hardclock(frame) { register struct callout *p1; register struct proc *p; - register int delta, needsoft; - extern int tickdelta; - extern long timedelta; + register int needsoft; + int time_update; + struct timeval newtime; + long ltemp; /* * Update real-time timeout queue. @@ -189,28 +407,142 @@ hardclock(frame) statclock(frame); /* - * Increment the time-of-day. The increment is normally just - * ``tick''. If the machine is one which has a clock frequency - * such that ``hz'' would not divide the second evenly into - * milliseconds, a periodic adjustment must be applied. Finally, - * if we are still adjusting the time (see adjtime()), - * ``tickdelta'' may also be added in. + * Increment the time-of-day */ ticks++; - delta = tick; - if (tickfix) { - tickfixcnt++; - if (tickfixcnt >= tickfixinterval) { - delta += tickfix; - tickfixcnt = 0; - } + newtime = time; + + if (timedelta == 0) { + time_update = tick; } - if (timedelta != 0) { - delta = tick + tickdelta; + else { + time_update = tick + tickdelta; timedelta -= tickdelta; } - BUMPTIME(&time, delta); - BUMPTIME(&mono_time, delta); + 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. + * + * 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 (newtime.tv_usec >= 1000000) { + newtime.tv_usec -= 1000000; + newtime.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 following code + * the overall gain is increased by a factor of 1.25. + */ + if (hz == 100) { + if (time_adj < 0) + time_adj -= -time_adj >> 2; + else + time_adj += time_adj >> 2; + } + /* + * 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 + * replacesd. + */ + 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; + + case TIME_OOP: + time_state = TIME_WAIT; + break; + + case TIME_WAIT: + if (!(time_status & (STA_INS | STA_DEL))) + time_state = TIME_OK; + break; + } + } + time = newtime; /* * Process callouts at a very low cpu priority, so we don't keep the @@ -345,33 +677,53 @@ int hzto(tv) struct timeval *tv; { - register long ticks, sec; + register unsigned long ticks; + register long sec, usec; int s; /* - * If number of microseconds will fit in 32 bit arithmetic, - * then compute number of microseconds to time and scale to - * ticks. Otherwise just compute number of hz in time, rounding - * times greater than representible to maximum value. (We must - * compute in microseconds, because hz can be greater than 1000, - * and thus tick can be less than one millisecond). + * 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. + * + * Otherwise, round the time difference down to the maximum + * representable value. * - * Delta times less than 14 hours can be computed ``exactly''. - * (Note that if hz would yeild a non-integral number of us per - * tick, i.e. tickfix is nonzero, timouts can be a tick longer - * than they should be.) Maximum value for any timeout in 10ms - * ticks is 250 days. + * If ints have 32 bits, then the maximum value for any timeout in + * 10ms ticks is 248 days. */ - s = splhigh(); + s = splclock(); sec = tv->tv_sec - time.tv_sec; - if (sec <= 0x7fffffff / 1000000 - 1) - ticks = ((tv->tv_sec - time.tv_sec) * 1000000 + - (tv->tv_usec - time.tv_usec)) / tick; - 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; + if (ticks > INT_MAX) + ticks = INT_MAX; return (ticks); } @@ -539,9 +891,8 @@ sysctl_clockrate(where, sizep) /* * Construct clockinfo structure. */ - clkinfo.tick = tick; - clkinfo.tickadj = tickadj; clkinfo.hz = hz; + clkinfo.tick = tick; clkinfo.profhz = profhz; clkinfo.stathz = stathz ? stathz : hz; return (sysctl_rdstruct(where, sizep, NULL, &clkinfo, sizeof(clkinfo))); |