Have a followup question on this.

It says in the man page that:

> When running as a boundary clock ... all of the ports share the same
hardware clock device.

And then:

> For this mode, the collection of clocks must be synchronized by an
external program, for example phc2sys
<http://manpages.ubuntu.com/manpages/cosmic/man8/phc2sys.8.html>(8) in
"automatic" mode.

I am confused about what this external program is supposed to do. If all
the ports share the same hardware clock device, then aren't these ports
synchronized already? Once ptp4l sets the PHC on a slave port, won't all
the other ports see the same exact time automatically? How can 2 clocks
that share the same hardware clock device be even out of sync?

On Tue, May 21, 2019 at 12:53 AM Richard Cochran <richardcoch...@gmail.com>
wrote:

> On Mon, May 20, 2019 at 12:31:07PM -0400, Sanjay Bhandari wrote:
> > > With the *-a* option, the clocks to synchronize are fetched from the
> > running *ptp4l* daemon and the direction of synchronization automatically
> > follows changes of the PTP port states.
> >
> > Is this talking about multiple PTP ports (clocks)?
>
> Yes.
>
> > Is it saying that
> > phc2sys will follow the roles decided by the PTP protocol, and set the
> PHC
> > on ports that happen to be masters from a port that is a slave?
>
> You got it!
>
> > All I can
> > think is that this applies when the node is a boundary clock. Can someone
> > comment?
>
> Um hm.
>
> > How does this play with the scenario where the node is the grandmaster?
> > What is the direction of time synchronization in that case?
>
> It picks the first interface from the ptp4l command line (or
> config. file) as the master clock.
>
> With -r -r you can also serve CLOCK_REALTIME.
>
> HTH,
> Richard
>
_______________________________________________
Linuxptp-users mailing list
Linuxptp-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linuxptp-users

Reply via email to