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phc2sys: don't zero clock frequency on start. 

Instead of always starting at zero frequency offset, read the currently
stored value on start and pass it to the servo. As the read may silently
fail and return zero, set the clock frequency back to the read value to
make sure it's always equal to the actual frequency of the clock.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
master
Miroslav Lichvar 2013-01-14 17:09:14 +01:00 committed by Richard Cochran
parent 2d4b2f1640
commit fc1a695493
1 changed files with 18 additions and 2 deletions
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20
phc2sys.c
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@ -76,6 +76,18 @@ static void clock_ppb(clockid_t clkid, double ppb)
fprintf(stderr, "failed to adjust the clock: %m\n"); fprintf(stderr, "failed to adjust the clock: %m\n");
} }
static double clock_ppb_read(clockid_t clkid)
{
double f = 0.0;
struct timex tx;
memset(&tx, 0, sizeof(tx));
if (clock_adjtime(clkid, &tx) < 0)
fprintf(stderr, "failed to read out the clock frequency adjustment: %m\n");
else
f = tx.freq / 65.536;
return f;
}
static void clock_step(clockid_t clkid, int64_t ns) static void clock_step(clockid_t clkid, int64_t ns)
{ {
struct timex tx; struct timex tx;
@ -271,6 +283,7 @@ int main(int argc, char *argv[])
char *device = NULL, *progname, *ethdev = NULL; char *device = NULL, *progname, *ethdev = NULL;
clockid_t src = CLOCK_INVALID; clockid_t src = CLOCK_INVALID;
int c, phc_readings = 5, phc_rate = 1, sync_offset = 0; int c, phc_readings = 5, phc_rate = 1, sync_offset = 0;
double ppb;
struct clock dst_clock = { struct clock dst_clock = {
.clkid = CLOCK_REALTIME, .clkid = CLOCK_REALTIME,
.log_file = stdout .log_file = stdout
@ -351,9 +364,12 @@ int main(int argc, char *argv[])
perror("clock_settime"); perror("clock_settime");
} }
clock_ppb(dst_clock.clkid, 0.0); ppb = clock_ppb_read(dst_clock.clkid);
/* The reading may silently fail and return 0, reset the frequency to
make sure ppb is the actual frequency of the clock. */
clock_ppb(dst_clock.clkid, ppb);
dst_clock.servo = servo_create(CLOCK_SERVO_PI, 0.0, max_ppb, 0); dst_clock.servo = servo_create(CLOCK_SERVO_PI, -ppb, max_ppb, 0);
if (device) if (device)
return do_pps_loop(&dst_clock, device); return do_pps_loop(&dst_clock, device);