This is helpful, thank you Ed.
Thanks,
Nemo
On Friday, 16 June, 2023 at 03:08:38 pm GMT-4, Ed Branch
<bra...@arlut.utexas.edu> wrote:
TLDR: It could also be the GM.
I see this on embedded networks, ie. the whole network including the GM
is on the same power switch, it all comes up together, and none of the
RTC's have battery backup.
Maybe the "GM" is just another embedded computer that gets time from GPS
or something like that. So the "GM" starts serving time over PTP
starting at the epoch, everything sync's to it, then the GM jumps when
it gets GPS lock.
Alternately, the GM just takes longer to boot for whatever reason. So
some random host is selected as master, serving the epoch over PTP, and
all the other hosts sync to that. Then, when the GM starts serving the
real time, the other hosts switch to it. But again, phc2sys has already
sync'd to the wrong time.
- Ed
On 6/16/23 10:19, Nemo Crypto wrote:
> Thank you Ed!
> I am using -w option but not -S. I now understand why the clock step is
> not happening. But with -w phc2sys should start only after ptp4l, isn't it?
> If yes, then why would this happen - "the clock has jumped from the
> epoch after phc2sys started".
>
> The only way is probably that "-w" option is not effective?
>
>
> Thanks,
> Nemo
>
>
> On Friday, 16 June, 2023 at 09:33:23 am GMT-4, Ed Branch
> <bra...@arlut.utexas.edu> wrote:
>
>
> You need either of:
>
> 1) a battery backup for the real-time clock so that it starts at a
> reasonable time.
> 2) Use -w option to phc2sys so that it waits until ptp4l is synchronized.
> 3) Use the -S option to phc2sys so that it steps the clock if the offset
> is above some threshold.
>
> By default, phc2sys will step the clock only once at startup, but here
> the clock has jumped from the epoch after phc2sys started. It would take
> a very long time (530 years in this case) to adjust for that without
> stepping the clock.
>
> - Ed
>
> On 6/15/23 19:06, Nemo Crypto wrote:
> > Hi LinuxPTPUsers,
> >
> > I have this weird problem sometimes with phc2syc. Please look at the log
> > below, ptp4l service is perfectly okay. But the phc2sys is stuck
> > (although it measures the offset correctly) and not adjusting the system
> > time for some reason. Why would this happen? Waiting for more than 30
> > minutes didn't fix this problem.
> >
> > Several reboots fixes the issue.
> >
> > 1970-01-01T00:05:09.600718+00:00 phc2sys: [304.725] CLOCK_REALTIME
> phc offset -1686774497008453238 s2 freq -100000000 delay 1372
> >
> > 1970-01-01T00:05:09.628181+00:00 ptp4l: [304.752] master offset
> 198 s3 freq -35590 path delay 323
> >
> > 1970-01-01T00:05:10.611304+00:00 phc2sys: [305.735] CLOCK_REALTIME
> phc offset -1686774496916583694 s2 freq -100000000 delay 1372
> >
> > 1970-01-01T00:05:10.728644+00:00 ptp4l: [305.853] master offset
> -63 s3 freq -35792 path delay 323
> >
> > 1970-01-01T00:05:11.618971+00:00 phc2sys: [306.743] CLOCK_REALTIME
> phc offset -1686774496824974153 s2 freq -100000000 delay 1373
> >
> > 1970-01-01T00:05:11.829106+00:00 ptp4l: [306.953] master offset
> -121 s3 freq -35869 path delay 323
> >
> > 1970-01-01T00:05:12.717043+00:00 phc2sys: [307.841] CLOCK_REALTIME
> phc offset -1686774496725151408 s2 freq -100000000 delay 1408
> >
> > 1970-01-01T00:05:12.929540+00:00 ptp4l: [308.054] master offset
> 111 s3 freq -35673 path delay 323
> >
> > 1970-01-01T00:05:13.721458+00:00 phc2sys: [308.846] CLOCK_REALTIME
> phc offset -1686774496633835940 s2 freq -100000000 delay 1373
> >
> > 1970-01-01T00:05:14.030032+00:00 ptp4l: [309.154] master offset
> -112 s3 freq -35863 path delay 323
> >
> >
> >
> > Thanks,
> > Nemo
>
> >
> >
> >
> >
> >
> >
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