diff options
Diffstat (limited to 'sys/kern/kern_clock.c')
| -rw-r--r-- | sys/kern/kern_clock.c | 379 |
1 files changed, 252 insertions, 127 deletions
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c index b1f3bb0..3a6b580 100644 --- a/sys/kern/kern_clock.c +++ b/sys/kern/kern_clock.c @@ -36,7 +36,7 @@ * SUCH DAMAGE. * * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 - * $Id: kern_clock.c,v 1.27 1996/10/10 10:25:03 bde Exp $ + * $Id: kern_clock.c,v 1.28 1996/10/25 13:01:56 bde Exp $ */ /* Portions of this software are covered by the following: */ @@ -162,7 +162,7 @@ volatile struct timeval time; volatile struct timeval mono_time; /* - * Phase-lock loop (PLL) definitions + * Phase/frequency-lock loop (PLL/FLL) definitions * * The following variables are read and set by the ntp_adjtime() system * call. @@ -173,7 +173,7 @@ volatile struct timeval mono_time; * 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 + * 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. @@ -205,7 +205,7 @@ 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 + * 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. * @@ -219,7 +219,8 @@ long time_esterror = MAXPHASE; /* estimated error (us) */ * daemon. * * time_adj is the adjustment added to the value of tick at each timer - * interrupt and is recomputed at each timer interrupt. + * 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 @@ -227,26 +228,28 @@ long time_esterror = MAXPHASE; /* estimated error (us) */ * increases. */ static long time_phase = 0; /* phase offset (scaled us) */ -long time_freq = 0; /* frequency offset (scaled ppm) */ +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. + * 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(). + * 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 measured by this - * 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 measured by - * this filter. + * 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 @@ -261,9 +264,6 @@ static long time_reftime = 0; /* time at last adjustment (s) */ * 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. */ @@ -337,10 +337,9 @@ long clock_cpu = 0; /* CPU clock adjust */ * 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 + * 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 @@ -348,9 +347,11 @@ long clock_cpu = 0; /* CPU clock adjust */ * 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. + * 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. */ @@ -367,24 +368,48 @@ hardupdate(offset) 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 (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_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) @@ -514,35 +539,55 @@ hardclock(frame) * 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. + * 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 >> - (SHIFT_KG + time_constant); + 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 >> - (SHIFT_KG + time_constant); - time_offset -= ltemp; - time_adj = ltemp << - (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE); - } -#ifdef PPS_SYNC + 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); + } + /* - * Gnaw on the watchdog counter and update the frequency - * computed by the pll and the PPS signal. + * 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; @@ -561,6 +606,7 @@ hardclock(frame) 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 @@ -577,6 +623,7 @@ hardclock(frame) 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 @@ -998,21 +1045,29 @@ 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*/ -#if 0 -/* This code is completely bogus; if anybody ever wants to use it, get - * the current version from Dave Mills. */ - +#ifdef PPS_SYNC /* - * hardpps() - discipline CPU clock oscillator to external pps signal + * 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 + * 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 designated PPS signal transition. + * 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, usec) @@ -1023,6 +1078,76 @@ hardpps(tvp, usec) 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; + if (pps_tf[0] > pps_tf[1]) { + if (pps_tf[1] > pps_tf[2]) { + pps_offset = pps_tf[1]; /* 0 1 2 */ + v_usec = pps_tf[0] - pps_tf[2]; + } else if (pps_tf[2] > pps_tf[0]) { + pps_offset = pps_tf[0]; /* 2 0 1 */ + v_usec = pps_tf[2] - pps_tf[1]; + } else { + pps_offset = pps_tf[2]; /* 0 2 1 */ + v_usec = pps_tf[0] - pps_tf[1]; + } + } else { + if (pps_tf[1] < pps_tf[2]) { + pps_offset = pps_tf[1]; /* 2 1 0 */ + v_usec = pps_tf[2] - pps_tf[0]; + } else if (pps_tf[2] < pps_tf[0]) { + pps_offset = pps_tf[0]; /* 1 0 2 */ + v_usec = pps_tf[1] - pps_tf[2]; + } else { + pps_offset = pps_tf[2]; /* 1 2 0 */ + v_usec = pps_tf[1] - pps_tf[0]; + } + } + 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 @@ -1034,7 +1159,7 @@ hardpps(tvp, usec) * the values returned and used here are correct. */ bigtick = (long)tick << SHIFT_USEC; - pps_usec -= ntp_pll.ybar; + pps_usec -= pps_freq; if (pps_usec >= bigtick) pps_usec -= bigtick; if (pps_usec < 0) @@ -1044,7 +1169,7 @@ hardpps(tvp, usec) if (pps_count < (1 << pps_shift)) return; pps_count = 0; - ntp_pll.calcnt++; + pps_calcnt++; u_usec = usec << SHIFT_USEC; v_usec = pps_usec - u_usec; if (v_usec >= bigtick >> 1) @@ -1052,9 +1177,9 @@ hardpps(tvp, usec) if (v_usec < -(bigtick >> 1)) v_usec += bigtick; if (v_usec < 0) - v_usec = -(-v_usec >> ntp_pll.shift); + v_usec = -(-v_usec >> pps_shift); else - v_usec = v_usec >> ntp_pll.shift; + v_usec = v_usec >> pps_shift; pps_usec = u_usec; cal_sec = tvp->tv_sec; cal_usec = tvp->tv_usec; @@ -1077,91 +1202,91 @@ hardpps(tvp, usec) 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; + || 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 - * signal. The median sample becomes the offset estimate; the - * difference between the other two samples becomes the - * dispersion estimate. + * frequency. The median sample becomes the frequency offset + * estimate; the difference between the other two samples + * becomes the frequency dispersion (stability) 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]; + pps_ff[2] = pps_ff[1]; + pps_ff[1] = pps_ff[0]; + pps_ff[0] = v_usec; + if (pps_ff[0] > pps_ff[1]) { + if (pps_ff[1] > pps_ff[2]) { + u_usec = pps_ff[1]; /* 0 1 2 */ + v_usec = pps_ff[0] - pps_ff[2]; + } else if (pps_ff[2] > pps_ff[0]) { + u_usec = pps_ff[0]; /* 2 0 1 */ + v_usec = pps_ff[2] - pps_ff[1]; } else { - u_usec = pps_mf[2]; /* 0 2 1 */ - v_usec = pps_mf[0] - pps_mf[1]; + u_usec = pps_ff[2]; /* 0 2 1 */ + v_usec = pps_ff[0] - pps_ff[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]; + if (pps_ff[1] < pps_ff[2]) { + u_usec = pps_ff[1]; /* 2 1 0 */ + v_usec = pps_ff[2] - pps_ff[0]; + } else if (pps_ff[2] < pps_ff[0]) { + u_usec = pps_ff[0]; /* 1 0 2 */ + v_usec = pps_ff[1] - pps_ff[2]; } else { - u_usec = pps_mf[2]; /* 1 2 0 */ - v_usec = pps_mf[1] - pps_mf[0]; + u_usec = pps_ff[2]; /* 1 2 0 */ + v_usec = pps_ff[1] - pps_ff[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. + * 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) - ntp_pll.disp; + v_usec = (v_usec >> 1) - pps_stabil; if (v_usec < 0) - ntp_pll.disp -= -v_usec >> PPS_AVG; + pps_stabil -= -v_usec >> PPS_AVG; else - ntp_pll.disp += v_usec >> PPS_AVG; - if (ntp_pll.disp > pps_dispmax) { - ntp_pll.discnt++; + pps_stabil += v_usec >> PPS_AVG; + if (pps_stabil > MAXFREQ >> 2) { + pps_stbcnt++; + time_status |= STA_PPSWANDER; 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; + 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 + * 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; - } + 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 - ntp_pll.intcnt++; + pps_intcnt++; } #endif /* PPS_SYNC */ |
