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Don't use time_offset as a leaky bucket variable in hardpps(), this

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resulted in vastly optimistic offset values reported to userland
(typically a factor 40+ too small).  Apart from that, the code had
two sign-bugs.

Apply the hardpps() phase with the right sign with a simply
scaling by integration interval.  (This may be too stiff at
long integration intervals, see below).

Allow pps_shiftmax to be reduced again.

Before this, the phase lock in hardpps() were broken, but due to
two bugs mostly cancelling out, it would end up basically working
with a large stochastic component.  Now it behaves as one would
expect: smooth and quiet.

It seems that pps_shiftmax above 7..9 somewhere makes the phaselock
too weak to hold onto random walk phase errors from a HP-105 OCXO,
which basically means that it is too weak for real-life use with
such integration times.  This is yet to be resolved.

Submitted to:	Prof. Dave "NTP" Mills.
Tested by:	Terje Mathisen <Terje.Mathisen@hda.hydro.com>
This commit is contained in:
Poul-Henning Kamp 1999-12-29 14:39:24 +00:00
parent 4712894e59
commit 19c5221906
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=55219
1 changed files with 18 additions and 15 deletions
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33
sys/kern/kern_ntptime.c
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@ -27,6 +27,8 @@
* 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.
*
* $FreeBSD$
*/
#include "opt_ntp.h"
@ -398,7 +400,7 @@ void
ntp_update_second(struct timecounter *tcp)
{
u_int32_t *newsec;
l_fp ftemp, time_adj; /* 32/64-bit temporaries */
l_fp time_adj; /* 32/64-bit temporaries */
newsec = &tcp->tc_offset_sec;
/*
@ -477,18 +479,18 @@ ntp_update_second(struct timecounter *tcp)
* value is in effect scaled by the clock frequency,
* since the adjustment is added at each tick interrupt.
*/
ftemp = time_offset;
time_adj = time_offset;
#ifdef PPS_SYNC
if (time_status & STA_PPSTIME && time_status &
STA_PPSSIGNAL)
L_RSHIFT(ftemp, PPS_FAVG);
else
L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) {
L_RSHIFT(time_adj, pps_shift);
} else {
L_RSHIFT(time_adj, SHIFT_PLL + time_constant);
L_SUB(time_offset, time_adj);
}
#else
L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
L_RSHIFT(time_adj, SHIFT_PLL + time_constant);
L_SUB(time_offset, time_adj);
#endif /* PPS_SYNC */
time_adj = ftemp;
L_SUB(time_offset, ftemp);
L_ADD(time_adj, time_freq);
tcp->tc_adjustment = time_adj;
#ifdef PPS_SYNC
@ -728,10 +730,7 @@ hardpps(tsp, nsec)
time_status |= STA_PPSJITTER;
pps_jitcnt++;
} else if (time_status & STA_PPSTIME) {
L_LINT(ftemp, v_nsec);
L_SUB(ftemp, time_offset);
L_RSHIFT(ftemp, pps_shift);
L_SUB(time_offset, ftemp);
L_LINT(time_offset, -v_nsec);
}
pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
u_sec = pps_tf[0].tv_sec - pps_lastsec;
@ -788,7 +787,11 @@ hardpps(tsp, nsec)
} else {
pps_intcnt++;
}
if (pps_intcnt >= 4) {
if (pps_shift > pps_shiftmax) {
/* If we lowered pps_shiftmax */
pps_shift = pps_shiftmax;
pps_intcnt = 0;
} else if (pps_intcnt >= 4) {
pps_intcnt = 4;
if (pps_shift < pps_shiftmax) {
pps_shift++;