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Create a separate pps_offset variable to use for applying the

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hardpps() produced offset component.  This is tested and behaved
stable with frequency offsets from -338.05 to +499.91 PPM.

Interestingly the machine I tested this on would fail if the clock
were slower than 14.3132 MHz whereas it was perfectly happy to run
at 16.384 MHz, in other words [-340PPM ... +14.4%]

Make pps_shift tweakable with sysctl.
This commit is contained in:
Poul-Henning Kamp 2000-01-04 12:04:39 +00:00
parent 8ac810799b
commit 6a77f60d4a
1 changed files with 8 additions and 1 deletions
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9
sys/kern/kern_ntptime.c
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@ -163,6 +163,7 @@ static l_fp time_freq; /* frequency offset (ns/s) */
#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
static struct timespec pps_tf[3]; /* phase median filter */
static l_fp pps_offset; /* time offset (ns) */
static l_fp pps_freq; /* scaled frequency offset (ns/s) */
static long pps_fcount; /* frequency accumulator */
static long pps_jitter; /* nominal jitter (ns) */
@ -245,6 +246,7 @@ SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
#ifdef PPS_SYNC
SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
#endif
/*
* ntp_adjtime() - NTP daemon application interface
@ -479,15 +481,19 @@ ntp_update_second(struct timecounter *tcp)
* value is in effect scaled by the clock frequency,
* since the adjustment is added at each tick interrupt.
*/
time_adj = time_offset;
#ifdef PPS_SYNC
/* XXX even if signal dies we should finish adjustment ? */
if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) {
time_adj = pps_offset;
L_RSHIFT(time_adj, pps_shift);
L_SUB(pps_offset, time_adj);
} else {
time_adj = time_offset;
L_RSHIFT(time_adj, SHIFT_PLL + time_constant);
L_SUB(time_offset, time_adj);
}
#else
time_adj = time_offset;
L_RSHIFT(time_adj, SHIFT_PLL + time_constant);
L_SUB(time_offset, time_adj);
#endif /* PPS_SYNC */
@ -731,6 +737,7 @@ hardpps(tsp, nsec)
pps_jitcnt++;
} else if (time_status & STA_PPSTIME) {
L_LINT(time_offset, -v_nsec);
L_LINT(pps_offset, -v_nsec);
}
pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
u_sec = pps_tf[0].tv_sec - pps_lastsec;