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Add non-PPS mode to phc2sys. 

As some PHC hardware/drivers don't provide PPS, it may be useful to keep the
system clock synchronized to PHC via clock_gettime(). While the precision
of the clock is only in microsecond range, the error seems to be quite stable.

The -d parameter now can be omitted if -s is provided.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
master
Richard Cochran 2012-08-29 15:29:43 +02:00
parent afd2a50b5b
commit 998093b6f7
1 changed files with 66 additions and 49 deletions
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115
phc2sys.c
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@ -85,33 +85,36 @@ static void clock_step(clockid_t clkid, int64_t ns)
fprintf(stderr, "failed to step clock: %m\n");
}
static int64_t read_phc(clockid_t clkid, clockid_t sysclk, int rdelay)
static int read_phc(clockid_t clkid, clockid_t sysclk, int rdelay, int64_t *offset, uint64_t *ts)
{
int64_t offset = 0;
struct timespec tsrc, tdst;
if (clkid == CLOCK_INVALID) {
return 0;
}
if (rdelay) {
struct timespec tsrc, tdst;
if (clock_gettime(clkid, &tsrc))
perror("clock_gettime");
if (clock_gettime(sysclk, &tdst))
perror("clock_gettime");
offset = tdst.tv_sec * NS_PER_SEC - tsrc.tv_sec * NS_PER_SEC +
tdst.tv_nsec - tsrc.tv_nsec - rdelay;
if (clock_gettime(clkid, &tsrc)) {
perror("clock_gettime");
return 0;
}
return offset;
if (clock_gettime(sysclk, &tdst)) {
perror("clock_gettime");
return 0;
}
*offset = tdst.tv_sec * NS_PER_SEC - tsrc.tv_sec * NS_PER_SEC +
tdst.tv_nsec - tsrc.tv_nsec - rdelay;
*ts = tdst.tv_sec * NS_PER_SEC + tdst.tv_nsec;
return 1;
}
struct servo {
uint64_t last_ts;
double drift;
enum {
PPS_0, PPS_1, PPS_2, PPS_3, PPS_N
SAMPLE_0, SAMPLE_1, SAMPLE_2, SAMPLE_3, SAMPLE_N
} state;
};
@ -119,42 +122,34 @@ static struct servo servo;
static void do_servo(struct servo *srv,
clockid_t src, clockid_t dst,
uint64_t ts, double kp, double ki, int rdelay)
int64_t offset, uint64_t ts, double kp, double ki)
{
double ki_term, ppb;
int64_t delta, offset, phc;
int64_t delta;
offset = ts % NS_PER_SEC;
if (offset > NS_PER_SEC / 2) {
offset -= NS_PER_SEC;
}
phc = read_phc(src, dst, rdelay);
printf("s%d %lld.%09llu offset %9lld phc %9lld drift %.2f\n",
srv->state, ts / NS_PER_SEC, ts % NS_PER_SEC,
offset, phc, srv->drift);
printf("s%d %lld.%09llu drift %.2f\n",
srv->state, ts / NS_PER_SEC, ts % NS_PER_SEC, srv->drift);
switch (srv->state) {
case PPS_0:
case SAMPLE_0:
clock_ppb(dst, 0.0);
srv->state = PPS_1;
srv->state = SAMPLE_1;
break;
case PPS_1:
srv->state = PPS_2;
case SAMPLE_1:
srv->state = SAMPLE_2;
break;
case PPS_2:
case SAMPLE_2:
delta = ts - srv->last_ts;
offset = delta - NS_PER_SEC;
srv->drift = offset;
clock_ppb(dst, -offset);
srv->state = PPS_3;
srv->state = SAMPLE_3;
break;
case PPS_3:
case SAMPLE_3:
clock_step(dst, -offset);
srv->state = PPS_N;
srv->state = SAMPLE_N;
break;
case PPS_N:
case SAMPLE_N:
ki_term = ki * offset;
ppb = kp * offset + srv->drift + ki_term;
if (ppb < min_ppb) {
@ -171,10 +166,10 @@ static void do_servo(struct servo *srv,
srv->last_ts = ts;
}
static uint64_t read_pps(int fd)
static int read_pps(int fd, int64_t *offset, uint64_t *ts)
{
struct pps_fdata pfd;
uint64_t ts;
pfd.timeout.sec = 10;
pfd.timeout.nsec = 0;
pfd.timeout.flags = ~PPS_TIME_INVALID;
@ -182,9 +177,15 @@ static uint64_t read_pps(int fd)
perror("ioctl PPS_FETCH");
return 0;
}
ts = pfd.info.assert_tu.sec * NS_PER_SEC;
ts += pfd.info.assert_tu.nsec;
return ts;
*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)
@ -208,8 +209,9 @@ 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 ts;
int c, fd, rdelay = 0;
uint64_t pps_ts, phc_ts;
int64_t pps_offset, phc_offset;
int c, fd = 0, rdelay = 0;
/* Process the command line arguments. */
progname = strrchr(argv[0], '/');
@ -243,14 +245,16 @@ int main(int argc, char *argv[])
}
}
if (!device || dst == CLOCK_INVALID) {
if (!(device || src != CLOCK_INVALID) || dst == CLOCK_INVALID) {
usage(progname);
return -1;
}
fd = open(device, O_RDONLY);
if (fd < 0) {
fprintf(stderr, "cannot open %s: %m\n", device);
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;
@ -260,8 +264,21 @@ int main(int argc, char *argv[])
perror("clock_settime");
}
while (1) {
ts = read_pps(fd);
do_servo(&servo, src, dst, ts, kp, ki, rdelay);
if (fd > 0) {
if (!read_pps(fd, &pps_offset, &pps_ts))
continue;
printf("pps %9lld ", pps_offset);
} else
usleep(1000000);
if (!read_phc(src, dst, rdelay, &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;
}