833 lines
26 KiB
C
833 lines
26 KiB
C
/***********************************************************************
|
|
* *
|
|
* Copyright (c) David L. Mills 1993-1999 *
|
|
* *
|
|
* 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. *
|
|
* *
|
|
**********************************************************************/
|
|
|
|
/*
|
|
* Adapted from the original sources for FreeBSD and timecounters by:
|
|
* Poul-Henning Kamp <phk@FreeBSD.org>.
|
|
*
|
|
* The 32bit version of the "LP" macros seems a bit past its "sell by"
|
|
* date so I have retained only the 64bit version and included it directly
|
|
* in this file.
|
|
*
|
|
* Only minor changes done to interface with the timecounters over in
|
|
* sys/kern/kern_clock.c. Some of the comments below may be (even more)
|
|
* confusing and/or plain wrong in that context.
|
|
*/
|
|
|
|
#include "opt_ntp.h"
|
|
|
|
#include <sys/param.h>
|
|
#include <sys/systm.h>
|
|
#include <sys/sysproto.h>
|
|
#include <sys/kernel.h>
|
|
#include <sys/proc.h>
|
|
#include <sys/time.h>
|
|
#include <sys/timex.h>
|
|
#include <sys/timepps.h>
|
|
#include <sys/sysctl.h>
|
|
|
|
/*
|
|
* Single-precision macros for 64-bit machines
|
|
*/
|
|
typedef long long l_fp;
|
|
#define L_ADD(v, u) ((v) += (u))
|
|
#define L_SUB(v, u) ((v) -= (u))
|
|
#define L_ADDHI(v, a) ((v) += (long long)(a) << 32)
|
|
#define L_NEG(v) ((v) = -(v))
|
|
#define L_RSHIFT(v, n) \
|
|
do { \
|
|
if ((v) < 0) \
|
|
(v) = -(-(v) >> (n)); \
|
|
else \
|
|
(v) = (v) >> (n); \
|
|
} while (0)
|
|
#define L_MPY(v, a) ((v) *= (a))
|
|
#define L_CLR(v) ((v) = 0)
|
|
#define L_ISNEG(v) ((v) < 0)
|
|
#define L_LINT(v, a) ((v) = (long long)(a) << 32)
|
|
#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
|
|
|
|
/*
|
|
* Generic NTP kernel interface
|
|
*
|
|
* These routines constitute the Network Time Protocol (NTP) interfaces
|
|
* for user and daemon application programs. The ntp_gettime() routine
|
|
* provides the time, maximum error (synch distance) and estimated error
|
|
* (dispersion) to client user application programs. The ntp_adjtime()
|
|
* routine is used by the NTP daemon to adjust the system clock to an
|
|
* externally derived time. The time offset and related variables set by
|
|
* this routine are used by other routines in this module to adjust the
|
|
* phase and frequency of the clock discipline loop which controls the
|
|
* system clock.
|
|
*
|
|
* When the kernel time is reckoned directly in nanoseconds (NTP_NANO
|
|
* defined), the time at each tick interrupt is derived directly from
|
|
* the kernel time variable. When the kernel time is reckoned in
|
|
* microseconds, (NTP_NANO undefined), the time is derived from the
|
|
* kernel time variable together with a variable representing the
|
|
* leftover nanoseconds at the last tick interrupt. In either case, the
|
|
* current nanosecond time is reckoned from these values plus an
|
|
* interpolated value derived by the clock routines in another
|
|
* architecture-specific module. The interpolation can use either a
|
|
* dedicated counter or a processor cycle counter (PCC) implemented in
|
|
* some architectures.
|
|
*
|
|
* Note that all routines must run at priority splclock or higher.
|
|
*/
|
|
|
|
/*
|
|
* Phase/frequency-lock loop (PLL/FLL) definitions
|
|
*
|
|
* The nanosecond clock discipline uses two variable types, time
|
|
* variables and frequency variables. Both types are represented as 64-
|
|
* bit fixed-point quantities with the decimal point between two 32-bit
|
|
* halves. On a 32-bit machine, each half is represented as a single
|
|
* word and mathematical operations are done using multiple-precision
|
|
* arithmetic. On a 64-bit machine, ordinary computer arithmetic is
|
|
* used.
|
|
*
|
|
* A time variable is a signed 64-bit fixed-point number in ns and
|
|
* fraction. It represents the remaining time offset to be amortized
|
|
* over succeeding tick interrupts. The maximum time offset is about
|
|
* 0.5 s and the resolution is about 2.3e-10 ns.
|
|
*
|
|
* 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
|
|
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
* |s s s| ns |
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
* | fraction |
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
*
|
|
* A frequency variable is a signed 64-bit fixed-point number in ns/s
|
|
* and fraction. It represents the ns and fraction to be added to the
|
|
* kernel time variable at each second. The maximum frequency offset is
|
|
* about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
|
|
*
|
|
* 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
|
|
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
* |s s s s s s s s s s s s s| ns/s |
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
* | fraction |
|
|
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
*/
|
|
/*
|
|
* The following variables establish the state of the PLL/FLL and the
|
|
* residual time and frequency offset of the local clock.
|
|
*/
|
|
#define SHIFT_PLL 4 /* PLL loop gain (shift) */
|
|
#define SHIFT_FLL 2 /* FLL loop gain (shift) */
|
|
|
|
static int time_state = TIME_OK; /* clock state */
|
|
static int time_status = STA_UNSYNC; /* clock status bits */
|
|
static long time_constant; /* poll interval (shift) (s) */
|
|
static long time_precision = 1; /* clock precision (ns) */
|
|
static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
|
|
static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
|
|
static long time_reftime; /* time at last adjustment (s) */
|
|
static long time_tick; /* nanoseconds per tick (ns) */
|
|
static l_fp time_offset; /* time offset (ns) */
|
|
static l_fp time_freq; /* frequency offset (ns/s) */
|
|
|
|
int ntp_mult;
|
|
int ntp_div;
|
|
#ifdef PPS_SYNC
|
|
/*
|
|
* The following variables are used when a pulse-per-second (PPS) signal
|
|
* is available and connected via a modem control lead. They establish
|
|
* the engineering parameters of the clock discipline loop when
|
|
* controlled by the PPS signal.
|
|
*/
|
|
#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
|
|
#define PPS_FAVGMAX 8 /* max freq avg interval (s) (shift) */
|
|
#define PPS_PAVG 4 /* phase avg interval (s) (shift) */
|
|
#define PPS_VALID 120 /* PPS signal watchdog max (s) */
|
|
#define MAXTIME 500000 /* max PPS error (jitter) (ns) */
|
|
#define MAXWANDER 500000 /* max PPS wander (ns/s/s) */
|
|
|
|
struct ppstime {
|
|
long sec; /* PPS seconds */
|
|
long nsec; /* PPS nanoseconds */
|
|
};
|
|
static struct ppstime pps_tf[3]; /* phase median filter */
|
|
static struct ppstime pps_filt; /* phase offset */
|
|
static l_fp pps_freq; /* scaled frequency offset (ns/s) */
|
|
static long pps_offacc; /* offset accumulator */
|
|
static long pps_fcount; /* frequency accumulator */
|
|
static long pps_jitter; /* scaled time dispersion (ns) */
|
|
static long pps_stabil; /* scaled frequency dispersion (ns/s) */
|
|
static long pps_lastsec; /* time at last calibration (s) */
|
|
static int pps_valid; /* signal watchdog counter */
|
|
static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
|
|
static int pps_intcnt; /* wander counter */
|
|
static int pps_offcnt; /* offset accumulator counter */
|
|
|
|
/*
|
|
* PPS signal quality monitors
|
|
*/
|
|
static long pps_calcnt; /* calibration intervals */
|
|
static long pps_jitcnt; /* jitter limit exceeded */
|
|
static long pps_stbcnt; /* stability limit exceeded */
|
|
static long pps_errcnt; /* calibration errors */
|
|
#endif /* PPS_SYNC */
|
|
/*
|
|
* End of phase/frequency-lock loop (PLL/FLL) definitions
|
|
*/
|
|
|
|
static void ntp_init(void);
|
|
static void hardupdate(long offset);
|
|
|
|
/*
|
|
* ntp_gettime() - NTP user application interface
|
|
*
|
|
* See the timex.h header file for synopsis and API description.
|
|
*/
|
|
static int
|
|
ntp_sysctl SYSCTL_HANDLER_ARGS
|
|
{
|
|
struct ntptimeval ntv; /* temporary structure */
|
|
struct timespec atv; /* nanosecond time */
|
|
|
|
nanotime(&atv);
|
|
ntv.time.tv_sec = atv.tv_sec;
|
|
ntv.time.tv_nsec = atv.tv_nsec;
|
|
ntv.maxerror = time_maxerror;
|
|
ntv.esterror = time_esterror;
|
|
ntv.time_state = time_state;
|
|
|
|
/*
|
|
* Status word error decode. If any of these conditions occur,
|
|
* an error is returned, instead of the status word. Most
|
|
* applications will care only about the fact the system clock
|
|
* may not be trusted, not about the details.
|
|
*
|
|
* Hardware or software error
|
|
*/
|
|
if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
|
|
|
|
/*
|
|
* PPS signal lost when either time or frequency synchronization
|
|
* requested
|
|
*/
|
|
(time_status & (STA_PPSFREQ | STA_PPSTIME) &&
|
|
!(time_status & STA_PPSSIGNAL)) ||
|
|
|
|
/*
|
|
* PPS jitter exceeded when time synchronization requested
|
|
*/
|
|
(time_status & STA_PPSTIME &&
|
|
time_status & STA_PPSJITTER) ||
|
|
|
|
/*
|
|
* PPS wander exceeded or calibration error when frequency
|
|
* synchronization requested
|
|
*/
|
|
(time_status & STA_PPSFREQ &&
|
|
time_status & (STA_PPSWANDER | STA_PPSERROR)))
|
|
ntv.time_state = TIME_ERROR;
|
|
return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
|
|
}
|
|
|
|
SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
|
|
SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
|
|
0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
|
|
|
|
SYSCTL_INT(_kern_ntp_pll, OID_AUTO, mult, CTLFLAG_RW, &ntp_mult, 0, "");
|
|
SYSCTL_INT(_kern_ntp_pll, OID_AUTO, div, CTLFLAG_RW, &ntp_div, 0, "");
|
|
|
|
/*
|
|
* ntp_adjtime() - NTP daemon application interface
|
|
*
|
|
* See the timex.h header file for synopsis and API description.
|
|
*/
|
|
#ifndef _SYS_SYSPROTO_H_
|
|
struct ntp_adjtime_args {
|
|
struct timex *tp;
|
|
};
|
|
#endif
|
|
|
|
int
|
|
ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap)
|
|
{
|
|
struct timex ntv; /* temporary structure */
|
|
long freq; /* frequency ns/s) */
|
|
int modes; /* mode bits from structure */
|
|
int s; /* caller priority */
|
|
int error;
|
|
|
|
error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
|
|
if (error)
|
|
return(error);
|
|
|
|
/*
|
|
* Update selected clock variables - only the superuser can
|
|
* change anything. Note that there is no error checking here on
|
|
* the assumption the superuser should know what it is doing.
|
|
*/
|
|
modes = ntv.modes;
|
|
if (modes)
|
|
error = suser(p->p_cred->pc_ucred, &p->p_acflag);
|
|
if (error)
|
|
return (error);
|
|
s = splclock();
|
|
if (modes & MOD_FREQUENCY) {
|
|
freq = (ntv.freq * 1000LL) >> 16;
|
|
if (freq > MAXFREQ)
|
|
L_LINT(time_freq, MAXFREQ);
|
|
else if (freq < -MAXFREQ)
|
|
L_LINT(time_freq, -MAXFREQ);
|
|
else
|
|
L_LINT(time_freq, freq);
|
|
|
|
#ifdef PPS_SYNC
|
|
pps_freq = time_freq;
|
|
#endif /* PPS_SYNC */
|
|
}
|
|
if (modes & MOD_MAXERROR)
|
|
time_maxerror = ntv.maxerror;
|
|
if (modes & MOD_ESTERROR)
|
|
time_esterror = ntv.esterror;
|
|
if (modes & MOD_STATUS) {
|
|
time_status &= STA_RONLY;
|
|
time_status |= ntv.status & ~STA_RONLY;
|
|
}
|
|
if (modes & MOD_TIMECONST) {
|
|
if (ntv.constant < 0)
|
|
time_constant = 0;
|
|
else if (ntv.constant > MAXTC)
|
|
time_constant = MAXTC;
|
|
else
|
|
time_constant = ntv.constant;
|
|
}
|
|
if (modes & MOD_NANO)
|
|
time_status |= STA_NANO;
|
|
if (modes & MOD_MICRO)
|
|
time_status &= ~STA_NANO;
|
|
if (modes & MOD_CLKB)
|
|
time_status |= STA_CLK;
|
|
if (modes & MOD_CLKA)
|
|
time_status &= ~STA_CLK;
|
|
if (modes & MOD_OFFSET) {
|
|
if (time_status & STA_NANO)
|
|
hardupdate(ntv.offset);
|
|
else
|
|
hardupdate(ntv.offset * 1000);
|
|
}
|
|
|
|
/*
|
|
* Retrieve all clock variables
|
|
*/
|
|
if (time_status & STA_NANO)
|
|
ntv.offset = L_GINT(time_offset);
|
|
else
|
|
ntv.offset = L_GINT(time_offset) / 1000;
|
|
ntv.freq = L_GINT((time_freq / 1000LL) << 16);
|
|
ntv.maxerror = time_maxerror;
|
|
ntv.esterror = time_esterror;
|
|
ntv.status = time_status;
|
|
ntv.constant = time_constant;
|
|
if (time_status & STA_NANO)
|
|
ntv.precision = time_precision;
|
|
else
|
|
ntv.precision = time_precision / 1000;
|
|
ntv.tolerance = MAXFREQ * SCALE_PPM;
|
|
#ifdef PPS_SYNC
|
|
ntv.shift = pps_shift;
|
|
ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
|
|
ntv.jitter = pps_jitter;
|
|
if (time_status & STA_NANO)
|
|
ntv.jitter = pps_jitter;
|
|
else
|
|
ntv.jitter = pps_jitter / 1000;
|
|
ntv.stabil = pps_stabil;
|
|
ntv.calcnt = pps_calcnt;
|
|
ntv.errcnt = pps_errcnt;
|
|
ntv.jitcnt = pps_jitcnt;
|
|
ntv.stbcnt = pps_stbcnt;
|
|
#endif /* PPS_SYNC */
|
|
splx(s);
|
|
|
|
error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
|
|
if (error)
|
|
return (error);
|
|
|
|
/*
|
|
* Status word error decode. See comments in
|
|
* ntp_gettime() routine.
|
|
*/
|
|
if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
|
|
(time_status & (STA_PPSFREQ | STA_PPSTIME) &&
|
|
!(time_status & STA_PPSSIGNAL)) ||
|
|
(time_status & STA_PPSTIME &&
|
|
time_status & STA_PPSJITTER) ||
|
|
(time_status & STA_PPSFREQ &&
|
|
time_status & (STA_PPSWANDER | STA_PPSERROR)))
|
|
p->p_retval[0] = TIME_ERROR;
|
|
else
|
|
p->p_retval[0] = time_state;
|
|
return (error);
|
|
}
|
|
|
|
/*
|
|
* second_overflow() - called after ntp_tick_adjust()
|
|
*
|
|
* This routine is ordinarily called immediately following the above
|
|
* routine ntp_tick_adjust(). While these two routines are normally
|
|
* combined, they are separated here only for the purposes of
|
|
* simulation.
|
|
*/
|
|
void
|
|
ntp_update_second(struct timecounter *tcp)
|
|
{
|
|
u_int32_t *newsec;
|
|
l_fp ftemp, time_adj; /* 32/64-bit temporaries */
|
|
|
|
newsec = &tcp->tc_offset_sec;
|
|
time_maxerror += MAXFREQ / 1000;
|
|
|
|
/*
|
|
* 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 nano_time() routine or
|
|
* external clock driver will insure that reported time
|
|
* is always monotonic.
|
|
*/
|
|
switch (time_state) {
|
|
|
|
/*
|
|
* No warning.
|
|
*/
|
|
case TIME_OK:
|
|
if (time_status & STA_INS)
|
|
time_state = TIME_INS;
|
|
else if (time_status & STA_DEL)
|
|
time_state = TIME_DEL;
|
|
break;
|
|
|
|
/*
|
|
* Insert second 23:59:60 following second
|
|
* 23:59:59.
|
|
*/
|
|
case TIME_INS:
|
|
if (!(time_status & STA_INS))
|
|
time_state = TIME_OK;
|
|
else if ((*newsec) % 86400 == 0) {
|
|
(*newsec)--;
|
|
time_state = TIME_OOP;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* Delete second 23:59:59.
|
|
*/
|
|
case TIME_DEL:
|
|
if (!(time_status & STA_DEL))
|
|
time_state = TIME_OK;
|
|
else if (((*newsec) + 1) % 86400 == 0) {
|
|
(*newsec)++;
|
|
time_state = TIME_WAIT;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* Insert second in progress.
|
|
*/
|
|
case TIME_OOP:
|
|
time_state = TIME_WAIT;
|
|
break;
|
|
|
|
/*
|
|
* Wait for status bits to clear.
|
|
*/
|
|
case TIME_WAIT:
|
|
if (!(time_status & (STA_INS | STA_DEL)))
|
|
time_state = TIME_OK;
|
|
}
|
|
|
|
/*
|
|
* Compute the total time adjustment for the next
|
|
* second in ns. The offset is reduced by a factor
|
|
* depending on FLL or PLL mode and whether the PPS
|
|
* signal is operating. Note that the value is in effect
|
|
* scaled by the clock frequency, since the adjustment
|
|
* is added at each tick interrupt.
|
|
*/
|
|
ftemp = time_offset;
|
|
#ifdef PPS_SYNC
|
|
if (time_status & STA_PPSTIME && time_status &
|
|
STA_PPSSIGNAL)
|
|
L_RSHIFT(ftemp, PPS_FAVG);
|
|
else if (time_status & STA_MODE)
|
|
#else
|
|
if (time_status & STA_MODE)
|
|
#endif /* PPS_SYNC */
|
|
L_RSHIFT(ftemp, SHIFT_FLL);
|
|
else
|
|
L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
|
|
time_adj = ftemp;
|
|
L_SUB(time_offset, ftemp);
|
|
L_ADD(time_adj, time_freq);
|
|
tcp->tc_adjustment = time_adj;
|
|
#ifdef PPS_SYNC
|
|
if (pps_valid > 0)
|
|
pps_valid--;
|
|
else
|
|
time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
|
|
STA_PPSWANDER | STA_PPSERROR);
|
|
#endif /* PPS_SYNC */
|
|
}
|
|
|
|
/*
|
|
* ntp_init() - initialize variables and structures
|
|
*
|
|
* This routine must be called after the kernel variables hz and tick
|
|
* are set or changed and before the next tick interrupt. In this
|
|
* particular implementation, these values are assumed set elsewhere in
|
|
* the kernel. The design allows the clock frequency and tick interval
|
|
* to be changed while the system is running. So, this routine should
|
|
* probably be integrated with the code that does that.
|
|
*/
|
|
static void
|
|
ntp_init()
|
|
{
|
|
|
|
/*
|
|
* The following variable must be initialized any time the
|
|
* kernel variable hz is changed.
|
|
*/
|
|
time_tick = NANOSECOND / hz;
|
|
|
|
/*
|
|
* The following variables are initialized only at startup. Only
|
|
* those structures not cleared by the compiler need to be
|
|
* initialized, and these only in the simulator. In the actual
|
|
* kernel, any nonzero values here will quickly evaporate.
|
|
*/
|
|
L_CLR(time_offset);
|
|
L_CLR(time_freq);
|
|
#ifdef PPS_SYNC
|
|
pps_filt.sec = pps_filt.nsec = 0;
|
|
pps_tf[0] = pps_tf[1] = pps_tf[2] = pps_filt;
|
|
pps_fcount = 0;
|
|
L_CLR(pps_freq);
|
|
#endif /* PPS_SYNC */
|
|
}
|
|
|
|
SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL)
|
|
|
|
/*
|
|
* hardupdate() - local clock update
|
|
*
|
|
* This routine is called by ntp_adjtime() to update the local clock
|
|
* 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
|
|
* 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 uncompensated quartz crystal oscillators and nominal update
|
|
* intervals less than 256 s, operation should be in phase-lock mode,
|
|
* where the loop is disciplined to phase. For update intervals greater
|
|
* than 1024 s, operation should be in frequency-lock mode, where the
|
|
* loop is disciplined to frequency. Between 256 s and 1024 s, the mode
|
|
* is selected by the STA_MODE status bit.
|
|
*/
|
|
static void
|
|
hardupdate(offset)
|
|
long offset; /* clock offset (ns) */
|
|
{
|
|
long ltemp, mtemp;
|
|
l_fp ftemp;
|
|
|
|
/*
|
|
* Select how the phase is to be controlled and from which
|
|
* source. If the PPS signal is present and enabled to
|
|
* discipline the time, the PPS offset is used; otherwise, the
|
|
* argument offset is used.
|
|
*/
|
|
ltemp = offset;
|
|
if (ltemp > MAXPHASE)
|
|
ltemp = MAXPHASE;
|
|
else if (ltemp < -MAXPHASE)
|
|
ltemp = -MAXPHASE;
|
|
if (!(time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL))
|
|
L_LINT(time_offset, ltemp);
|
|
|
|
/*
|
|
* Select how the frequency is to be controlled and in which
|
|
* mode (PLL or FLL). If the PPS signal is present and enabled
|
|
* to discipline the frequency, the PPS frequency is used;
|
|
* otherwise, the argument offset is used to compute it.
|
|
*/
|
|
if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
|
|
time_reftime = time_second;
|
|
return;
|
|
}
|
|
if (time_status & STA_FREQHOLD || time_reftime == 0)
|
|
time_reftime = time_second;
|
|
mtemp = time_second - time_reftime;
|
|
if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)
|
|
) {
|
|
L_LINT(ftemp, (ltemp << 4) / mtemp);
|
|
L_RSHIFT(ftemp, SHIFT_FLL + 4);
|
|
L_ADD(time_freq, ftemp);
|
|
time_status |= STA_MODE;
|
|
} else {
|
|
L_LINT(ftemp, ltemp);
|
|
L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
|
|
L_MPY(ftemp, mtemp);
|
|
L_ADD(time_freq, ftemp);
|
|
time_status &= ~STA_MODE;
|
|
}
|
|
time_reftime = time_second;
|
|
if (L_GINT(time_freq) > MAXFREQ)
|
|
L_LINT(time_freq, MAXFREQ);
|
|
else if (L_GINT(time_freq) < -MAXFREQ)
|
|
L_LINT(time_freq, -MAXFREQ);
|
|
}
|
|
|
|
#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 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 the intrinsic frequency error is cancelled
|
|
* out. The code requires the caller to capture the time and
|
|
* architecture-dependent hardware counter values in nanoseconds 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 the actual time and frequency variables, which
|
|
* are determined by this routine and updated atomically.
|
|
*/
|
|
void
|
|
hardpps(tsp, nsec)
|
|
struct timespec *tsp; /* time at PPS */
|
|
long nsec; /* hardware counter at PPS */
|
|
{
|
|
long u_sec, u_nsec, v_nsec; /* temps */
|
|
l_fp ftemp;
|
|
|
|
/*
|
|
* The signal is first processed by a frequency discriminator
|
|
* which rejects noise and input signals with frequencies
|
|
* outside the range 1 +-MAXFREQ PPS. If two hits occur in the
|
|
* same second, we ignore the later hit; if not and a hit occurs
|
|
* outside the range gate, keep the later hit but do not
|
|
* process it.
|
|
*/
|
|
time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
|
|
time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
|
|
pps_valid = PPS_VALID;
|
|
u_sec = tsp->tv_sec;
|
|
u_nsec = tsp->tv_nsec;
|
|
if (u_nsec >= (NANOSECOND >> 1)) {
|
|
u_nsec -= NANOSECOND;
|
|
u_sec++;
|
|
}
|
|
v_nsec = u_nsec - pps_tf[0].nsec;
|
|
if (u_sec == pps_tf[0].sec && v_nsec < -MAXFREQ) {
|
|
return;
|
|
}
|
|
pps_tf[2] = pps_tf[1];
|
|
pps_tf[1] = pps_tf[0];
|
|
pps_tf[0].sec = u_sec;
|
|
pps_tf[0].nsec = u_nsec;
|
|
|
|
/*
|
|
* Compute the difference between the current and previous
|
|
* counter values. If the difference exceeds 0.5 s, assume it
|
|
* has wrapped around, so correct 1.0 s. If the result exceeds
|
|
* the tick interval, the sample point has crossed a tick
|
|
* boundary during the last second, so correct the tick. Very
|
|
* intricate.
|
|
*/
|
|
u_nsec = nsec;
|
|
if (u_nsec > (NANOSECOND >> 1))
|
|
u_nsec -= NANOSECOND;
|
|
else if (u_nsec < -(NANOSECOND >> 1))
|
|
u_nsec += NANOSECOND;
|
|
pps_fcount += u_nsec;
|
|
if (v_nsec > MAXFREQ) {
|
|
return;
|
|
}
|
|
time_status &= ~STA_PPSJITTER;
|
|
|
|
/*
|
|
* A three-stage median filter is used to help denoise the PPS
|
|
* time. The median sample becomes the time offset estimate; the
|
|
* difference between the other two samples becomes the time
|
|
* dispersion (jitter) estimate.
|
|
*/
|
|
if (pps_tf[0].nsec > pps_tf[1].nsec) {
|
|
if (pps_tf[1].nsec > pps_tf[2].nsec) {
|
|
pps_filt = pps_tf[1]; /* 0 1 2 */
|
|
u_nsec = pps_tf[0].nsec - pps_tf[2].nsec;
|
|
} else if (pps_tf[2].nsec > pps_tf[0].nsec) {
|
|
pps_filt = pps_tf[0]; /* 2 0 1 */
|
|
u_nsec = pps_tf[2].nsec - pps_tf[1].nsec;
|
|
} else {
|
|
pps_filt = pps_tf[2]; /* 0 2 1 */
|
|
u_nsec = pps_tf[0].nsec - pps_tf[1].nsec;
|
|
}
|
|
} else {
|
|
if (pps_tf[1].nsec < pps_tf[2].nsec) {
|
|
pps_filt = pps_tf[1]; /* 2 1 0 */
|
|
u_nsec = pps_tf[2].nsec - pps_tf[0].nsec;
|
|
} else if (pps_tf[2].nsec < pps_tf[0].nsec) {
|
|
pps_filt = pps_tf[0]; /* 1 0 2 */
|
|
u_nsec = pps_tf[1].nsec - pps_tf[2].nsec;
|
|
} else {
|
|
pps_filt = pps_tf[2]; /* 1 2 0 */
|
|
u_nsec = pps_tf[1].nsec - pps_tf[0].nsec;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Nominal jitter is due to PPS signal noise and interrupt
|
|
* latency. If it exceeds the jitter limit, the sample is
|
|
* discarded. otherwise, if so enabled, the time offset is
|
|
* updated. The offsets are accumulated over the phase averaging
|
|
* interval to improve accuracy. The jitter is averaged only for
|
|
* performance monitoring. We can tolerate a modest loss of data
|
|
* here without degrading time accuracy.
|
|
*/
|
|
if (u_nsec > MAXTIME) {
|
|
time_status |= STA_PPSJITTER;
|
|
pps_jitcnt++;
|
|
} else if (time_status & STA_PPSTIME) {
|
|
pps_offacc -= pps_filt.nsec;
|
|
pps_offcnt++;
|
|
}
|
|
if (pps_offcnt >= (1 << PPS_PAVG)) {
|
|
if (time_status & STA_PPSTIME) {
|
|
L_LINT(time_offset, pps_offacc);
|
|
L_RSHIFT(time_offset, PPS_PAVG);
|
|
}
|
|
pps_offacc = 0;
|
|
pps_offcnt = 0;
|
|
}
|
|
pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
|
|
u_sec = pps_tf[0].sec - pps_lastsec;
|
|
if (ntp_div && ntp_mult) {
|
|
L_LINT(ftemp, (pps_filt.nsec));
|
|
L_RSHIFT(ftemp, ntp_div);
|
|
L_MPY(ftemp, ntp_mult);
|
|
L_ADD(pps_freq, ftemp);
|
|
if (time_status & STA_PPSFREQ)
|
|
time_freq = pps_freq;
|
|
return;
|
|
}
|
|
if (u_sec < (1 << pps_shift))
|
|
return;
|
|
|
|
/*
|
|
* At the end of the calibration interval the difference between
|
|
* the first and last counter values becomes the scaled
|
|
* frequency. It will later be divided by the length of the
|
|
* interval to determine the frequency update. If the frequency
|
|
* exceeds a sanity threshold, or if the actual calibration
|
|
* interval is not equal to the expected length, the data are
|
|
* discarded. We can tolerate a modest loss of data here without
|
|
* degrading frequency ccuracy.
|
|
*/
|
|
pps_calcnt++;
|
|
v_nsec = -pps_fcount;
|
|
pps_lastsec = pps_tf[0].sec;
|
|
pps_fcount = 0;
|
|
u_nsec = MAXFREQ << pps_shift;
|
|
if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
|
|
pps_shift)) {
|
|
time_status |= STA_PPSERROR;
|
|
pps_errcnt++;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If the actual calibration interval is not equal to the
|
|
* expected length, the data are discarded. If the wander is
|
|
* less than the wander threshold for four consecutive
|
|
* intervals, the interval is doubled; if it is greater than the
|
|
* threshold for four consecutive intervals, the interval is
|
|
* halved. The scaled frequency offset is converted to frequency
|
|
* offset. The stability metric is calculated as the average of
|
|
* recent frequency changes, but is used only for performance
|
|
* monitoring.
|
|
*/
|
|
L_LINT(ftemp, v_nsec);
|
|
L_RSHIFT(ftemp, pps_shift);
|
|
L_SUB(ftemp, pps_freq);
|
|
u_nsec = L_GINT(ftemp);
|
|
if (u_nsec > MAXWANDER) {
|
|
L_LINT(ftemp, MAXWANDER);
|
|
pps_intcnt--;
|
|
time_status |= STA_PPSWANDER;
|
|
pps_stbcnt++;
|
|
} else if (u_nsec < -MAXWANDER) {
|
|
L_LINT(ftemp, -MAXWANDER);
|
|
pps_intcnt--;
|
|
time_status |= STA_PPSWANDER;
|
|
pps_stbcnt++;
|
|
} else {
|
|
pps_intcnt++;
|
|
}
|
|
if (pps_intcnt >= 4) {
|
|
pps_intcnt = 4;
|
|
if (pps_shift < PPS_FAVGMAX) {
|
|
pps_shift++;
|
|
pps_intcnt = 0;
|
|
}
|
|
} else if (pps_intcnt <= -4) {
|
|
pps_intcnt = -4;
|
|
if (pps_shift > PPS_FAVG) {
|
|
pps_shift--;
|
|
pps_intcnt = 0;
|
|
}
|
|
}
|
|
if (u_nsec < 0)
|
|
u_nsec = -u_nsec;
|
|
pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
|
|
|
|
/*
|
|
* The frequency offset is averaged into the PPS frequency. If
|
|
* enabled, the system clock frequency is updated as well.
|
|
*/
|
|
L_RSHIFT(ftemp, PPS_FAVG);
|
|
L_ADD(pps_freq, ftemp);
|
|
u_nsec = L_GINT(pps_freq);
|
|
if (u_nsec > MAXFREQ)
|
|
L_LINT(pps_freq, MAXFREQ);
|
|
else if (u_nsec < -MAXFREQ)
|
|
L_LINT(pps_freq, -MAXFREQ);
|
|
if (time_status & STA_PPSFREQ)
|
|
time_freq = pps_freq;
|
|
}
|
|
#endif /* PPS_SYNC */
|