Estimate the local/master frequency ratio when free running.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>master
parent
83bd97be80
commit
cd8996ecb9
52
clock.c
52
clock.c
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@ -41,6 +41,13 @@
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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struct freq_estimator {
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tmv_t origin1;
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tmv_t ingress1;
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int max_count;
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int count;
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};
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struct clock {
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clockid_t clkid;
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struct servo *servo;
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@ -59,6 +66,7 @@ struct clock {
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tmv_t master_offset;
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tmv_t path_delay;
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struct mave *avg_delay;
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struct freq_estimator fest;
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tmv_t c1;
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tmv_t c2;
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tmv_t t1;
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@ -114,6 +122,46 @@ static int clock_master_lost(struct clock *c)
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return 1;
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}
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static enum servo_state clock_no_adjust(struct clock *c)
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{
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double ratio;
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struct freq_estimator *f = &c->fest;
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enum servo_state state = SERVO_UNLOCKED;
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/*
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* We have clock.t1 as the origin time stamp, and clock.t2 as
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* the ingress. The time at which the master sent the sync is:
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*
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* origin = origin_ts + path_delay + correction
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*
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* The ratio of the local clock freqency to the master clock
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* is estimated by:
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*
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* (ingress_2 - ingress_1) / (origin_2 - origin_1)
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*
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* Both of the origin time estimates include the path delay,
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* but we assume that the path delay is in fact constant.
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* By leaving out the path delay altogther, we can avoid the
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* error caused by our imperfect path delay measurement.
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*/
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f->count++;
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if (f->count < f->max_count) {
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return state;
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}
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if (f->ingress1) {
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ratio = (c->t2 - f->ingress1 + 0.0) /
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(c->t1 /*+c->path_delay*/ + c->c1 + c->c2 - f->origin1);
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pr_info("master offset %10lld s%d ratio %.9f path delay %10lld",
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c->master_offset, state, ratio, c->path_delay);
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}
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f->ingress1 = c->t2;
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f->origin1 = c->t1 /*+c->path_delay*/ + c->c1 + c->c2;
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f->count = 0;
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return state;
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}
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static void clock_ppb(clockid_t clkid, double ppb)
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{
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struct timex tx;
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@ -266,6 +314,7 @@ struct clock *clock_create(int phc_index, struct interface *iface, int count,
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}
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c->fault_timeout = FAULT_RESET_SECONDS;
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c->fest.max_count = 2;
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for (i = 0; i < count; i++) {
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c->port[i] = port_open(phc_index, timestamping, 1+i, &iface[i], c);
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@ -581,6 +630,9 @@ enum servo_state clock_synchronize(struct clock *c,
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if (!c->path_delay)
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return state;
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if (c->dds.free_running)
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return clock_no_adjust(c);
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adj = servo_sample(c->servo, c->master_offset, ingress, &state);
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pr_info("master offset %10lld s%d adj %+7.0f path delay %10lld",
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