Re: [Linuxptp-users] strange behavior with free_running regarding offset display

[Holzinger, A. (A. N. GmbH) <Axe...@al...>]

On Wed, 2015-01-07 at 16:38 +0100, Tino Keitel wrote:
> On Wed, 2015-01-07 at 16:30 +0100, Richard Cochran wrote:
> > Tino,
> >
> > On Wed, Jan 07, 2015 at 03:10:21PM +0100, Tino Keitel wrote:
> > > ptp4l[3620464.599]: rms 34999387468 max 34999407058 freq -
> > > 19592 +/-   0
> > > ptp4l[3620468.598]: rms 34999465846 max 34999485433 freq -
> > > 19595 +/-   7
> >
> > Max here is always positive. It is the absolute value
> > (magnitude) of the maximum offset during the interval.
> >
> > > Querying ptp4l using pmc gives this output (note the first
> > > offsetFromMaster value):
> > >
> > > $ pmc -u "get CURRENT_DATA_SET"
> > > sending: GET CURRENT_DATA_SET
> > > 	001b21.fffe.929906-0 seq 0 RESPONSE MANAGMENT
> > >       CURRENT_DATA_SET
> > > 		stepsRemoved     2
> > > 		offsetFromMaster -35000968295.0
> >
> > Here the plain offset is given.
> >
> > Both values show the offset error to be about 35 seconds, which
> > is the TAI/UTC offset. Probably your PHC driver sets its time
> > to the UTC system time when loading.
> 
> Hi Richard,
> 
> this sounds like it is normal behavior to show the offset to the
> PHC even if the PHC is not touched (free_running set to 1).
> 
> Regards,
> Tino

Rchard, Tino et al.

Does it make sense to print the offset error of the PHC when it's free running?

This value will always increase as the PHC drifts away over time, if it's free running. Shouldn't the message contain the true offset after calculation with the software offset? IMHO in free running mode it doesn't matter at which position the PHC starts (with or without UTC offset or any other weird position like zero = 01/01/1970).

Just my 0.02€
Axel