diff options
Diffstat (limited to 'sys/kern/kern_tc.c')
| -rw-r--r-- | sys/kern/kern_tc.c | 585 |
1 files changed, 575 insertions, 10 deletions
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c index 788e279..6b3f85f 100644 --- a/sys/kern/kern_tc.c +++ b/sys/kern/kern_tc.c @@ -36,9 +36,26 @@ * SUCH DAMAGE. * * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 - * $Id: kern_clock.c,v 1.4 1994/08/18 22:34:58 wollman Exp $ + * $Id: kern_clock.c,v 1.5 1994/08/27 16:14:26 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 <sys/param.h> #include <sys/systm.h> #include <sys/dkstat.h> @@ -46,9 +63,11 @@ #include <sys/kernel.h> #include <sys/proc.h> #include <sys/resourcevar.h> +#include <sys/timex.h> #include <vm/vm.h> #include <machine/cpu.h> +#include <machine/clock.h> #ifdef GPROF #include <sys/gmon.h> @@ -128,6 +147,238 @@ 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. + */ +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; +} + + + +/* * Initialize clock frequencies and start both clocks running. */ void @@ -207,18 +458,164 @@ hardclock(frame) statclock(frame); /* - * Increment the time-of-day. The increment is just ``tick'' unless - * we are still adjusting the clock; see adjtime(). + * Increment the time-of-day. */ ticks++; - if (timedelta == 0) - delta = tick; - else { - delta = tick + tickdelta; - timedelta -= tickdelta; + { + int time_update; + struct timeval newtime = time; + long ltemp; + + if (timedelta == 0) { + time_update = tick; + } else { + if (timedelta < 0) { + time_update = tick - tickdelta; + timedelta += tickdelta; + } else { + time_update = 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. + * + * 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 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 (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; + } + } + CPU_CLOCKUPDATE(&time, &newtime); } - BUMPTIME(&time, delta); - BUMPTIME(&mono_time, delta); /* * Process callouts at a very low cpu priority, so we don't keep the @@ -563,3 +960,171 @@ sysctl_clockrate(where, sizep) clkinfo.stathz = stathz ? stathz : hz; return (sysctl_rdstruct(where, sizep, NULL, &clkinfo, sizeof(clkinfo))); } + +/*#ifdef PPS_SYNC*/ +#if 0 +/* This code is completely bogus; if anybody ever wants to use it, get + * the current version from Dave Mills. */ + +/* + * 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 */ |
