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authorThorsten Lockert <tholo@cvs.openbsd.org>1996-01-29 23:05:12 +0000
committerThorsten Lockert <tholo@cvs.openbsd.org>1996-01-29 23:05:12 +0000
commit2b9936f3f7ab47a89436d4fa3b70e4c09dd2398e (patch)
tree981575b1c1e1e216672ebd7e22e7a24e38e71543 /sys/kern/kern_clock.c
parent0b76c30b56471d2de3bb8493b288a92682f7b9fe (diff)
Add kernel PLL for system clock
Add ntp_adjtime() and ntp_gettime() system calls Mostly stolen from FreeBSD
Diffstat (limited to 'sys/kern/kern_clock.c')
-rw-r--r--sys/kern/kern_clock.c441
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)));