linuxptp/phc2sys.c

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/**
* @file phc2sys.c
* @brief Utility program to synchronize two clocks via a PPS.
* @note Copyright (C) 2012 Richard Cochran <richardcochran@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <linux/pps.h>
#include <linux/ptp_clock.h>
#include "missing.h"
#define KP 0.7
#define KI 0.3
#define NS_PER_SEC 1000000000LL
#define max_ppb 512000
#define min_ppb -512000
static clockid_t clock_open(char *device)
{
int fd = open(device, O_RDWR);
if (fd < 0) {
fprintf(stderr, "cannot open %s: %m\n", device);
return CLOCK_INVALID;
}
return FD_TO_CLOCKID(fd);
}
static void clock_ppb(clockid_t clkid, double ppb)
{
struct timex tx;
memset(&tx, 0, sizeof(tx));
tx.modes = ADJ_FREQUENCY;
tx.freq = (long) (ppb * 65.536);
if (clock_adjtime(clkid, &tx) < 0)
fprintf(stderr, "failed to adjust the clock: %m\n");
}
static void clock_step(clockid_t clkid, int64_t ns)
{
struct timex tx;
int sign = 1;
if (ns < 0) {
sign = -1;
ns *= -1;
}
memset(&tx, 0, sizeof(tx));
tx.modes = ADJ_SETOFFSET | ADJ_NANO;
tx.time.tv_sec = sign * (ns / NS_PER_SEC);
tx.time.tv_usec = sign * (ns % NS_PER_SEC);
/*
* The value of a timeval is the sum of its fields, but the
* field tv_usec must always be non-negative.
*/
if (tx.time.tv_usec < 0) {
tx.time.tv_sec -= 1;
tx.time.tv_usec += 1000000000;
}
if (clock_adjtime(clkid, &tx) < 0)
fprintf(stderr, "failed to step clock: %m\n");
}
static int read_phc(clockid_t clkid, clockid_t sysclk, int rdelay, int readings, int64_t *offset, uint64_t *ts)
{
struct timespec tdst1, tdst2, tsrc;
int i;
int64_t interval, best_interval = INT64_MAX;
/* Pick the quickest clkid reading. */
for (i = 0; i < readings; i++) {
if (clock_gettime(sysclk, &tdst1) ||
clock_gettime(clkid, &tsrc) ||
clock_gettime(sysclk, &tdst2)) {
perror("clock_gettime");
return 0;
}
interval = (tdst2.tv_sec - tdst1.tv_sec) * NS_PER_SEC +
tdst2.tv_nsec - tdst1.tv_nsec;
if (best_interval > interval) {
best_interval = interval;
*offset = (tdst1.tv_sec - tsrc.tv_sec) * NS_PER_SEC +
tdst1.tv_nsec - tsrc.tv_nsec +
interval / 2 - rdelay;
*ts = tdst2.tv_sec * NS_PER_SEC + tdst2.tv_nsec;
}
}
return 1;
}
struct servo {
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uint64_t saved_ts;
int64_t saved_offset;
double drift;
enum {
SAMPLE_0, SAMPLE_1, SAMPLE_2, SAMPLE_3, SAMPLE_N
} state;
};
static struct servo servo;
static void do_servo(struct servo *srv,
clockid_t src, clockid_t dst,
int64_t offset, uint64_t ts, double kp, double ki)
{
double ki_term, ppb;
printf("s%d %lld.%09llu drift %.2f\n",
srv->state, ts / NS_PER_SEC, ts % NS_PER_SEC, srv->drift);
switch (srv->state) {
case SAMPLE_0:
clock_ppb(dst, 0.0);
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srv->saved_offset = offset;
srv->saved_ts = ts;
srv->state = SAMPLE_1;
break;
case SAMPLE_1:
srv->state = SAMPLE_2;
break;
case SAMPLE_2:
srv->state = SAMPLE_3;
break;
case SAMPLE_3:
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srv->drift = (offset - srv->saved_offset) * 1e9 /
(ts - srv->saved_ts);
clock_ppb(dst, -srv->drift);
clock_step(dst, -offset);
srv->state = SAMPLE_N;
break;
case SAMPLE_N:
ki_term = ki * offset;
ppb = kp * offset + srv->drift + ki_term;
if (ppb < min_ppb) {
ppb = min_ppb;
} else if (ppb > max_ppb) {
ppb = max_ppb;
} else {
srv->drift += ki_term;
}
clock_ppb(dst, -ppb);
break;
}
}
static int read_pps(int fd, int64_t *offset, uint64_t *ts)
{
struct pps_fdata pfd;
pfd.timeout.sec = 10;
pfd.timeout.nsec = 0;
pfd.timeout.flags = ~PPS_TIME_INVALID;
if (ioctl(fd, PPS_FETCH, &pfd)) {
perror("ioctl PPS_FETCH");
return 0;
}
*ts = pfd.info.assert_tu.sec * NS_PER_SEC;
*ts += pfd.info.assert_tu.nsec;
*offset = *ts % NS_PER_SEC;
if (*offset > NS_PER_SEC / 2)
*offset -= NS_PER_SEC;
return 1;
}
static void usage(char *progname)
{
fprintf(stderr,
"\n"
"usage: %s [options]\n\n"
" -c [device] slave clock device, default CLOCK_REALTIME\n"
" -d [device] master device, source of PPS events\n"
" -h prints this message and exits\n"
" -r [val] reading the PHC device takes 'val' nanoseconds\n"
" -s [device] set the time from this PHC device\n"
" -P [val] set proportional constant to 'val'\n"
" -I [val] set integration constant to 'val'\n"
" -R [val] set PHC update rate to 'val' Hz\n"
" -N [val] set number of PHC readings per update\n"
"\n",
progname);
}
int main(int argc, char *argv[])
{
double kp = KP, ki = KI;
char *device = NULL, *progname;
clockid_t src = CLOCK_INVALID, dst = CLOCK_REALTIME;
uint64_t pps_ts, phc_ts;
int64_t pps_offset, phc_offset;
int c, fd = 0, rdelay = 0, phc_readings = 5, phc_rate = 1;
/* Process the command line arguments. */
progname = strrchr(argv[0], '/');
progname = progname ? 1+progname : argv[0];
while (EOF != (c = getopt(argc, argv, "c:d:hr:s:P:I:R:N:"))) {
switch (c) {
case 'c':
dst = clock_open(optarg);
break;
case 'd':
device = optarg;
break;
case 'r':
rdelay = atoi(optarg);
break;
case 's':
src = clock_open(optarg);
break;
case 'P':
kp = atof(optarg);
break;
case 'I':
ki = atof(optarg);
break;
case 'R':
phc_rate = atoi(optarg);
break;
case 'N':
phc_readings = atoi(optarg);
break;
case 'h':
usage(progname);
return 0;
default:
usage(progname);
return -1;
}
}
if (!(device || src != CLOCK_INVALID) || dst == CLOCK_INVALID) {
usage(progname);
return -1;
}
if (device) {
fd = open(device, O_RDONLY);
if (fd < 0) {
fprintf(stderr, "cannot open %s: %m\n", device);
return -1;
}
}
if (src != CLOCK_INVALID) {
struct timespec now;
if (clock_gettime(src, &now))
perror("clock_gettime");
if (clock_settime(dst, &now))
perror("clock_settime");
}
while (1) {
if (fd > 0) {
if (!read_pps(fd, &pps_offset, &pps_ts))
continue;
printf("pps %9lld ", pps_offset);
} else
usleep(1000000 / phc_rate);
if (src != CLOCK_INVALID) {
if (!read_phc(src, dst, rdelay, phc_readings, &phc_offset, &phc_ts))
continue;
printf("phc %9lld ", phc_offset);
}
if (fd > 0)
do_servo(&servo, src, dst, pps_offset, pps_ts, kp, ki);
else
do_servo(&servo, src, dst, phc_offset, phc_ts, kp, ki);
}
return 0;
}