Re: [Linuxptp-users] Validating PTP

[Keller, J. E <jac...@in...>]

> -----Original Message-----
> From: Jim Baxter [mailto:jim...@uk...]
> Sent: Thursday, March 28, 2013 1:55 PM
> To: Keller, Jacob E
> Cc: lin...@li...
> Subject: Re: [Linuxptp-users] Validating PTP
> 
> 
> On 28/03/13 20:44, Keller, Jacob E wrote:
> >> -----Original Message-----
> >> From: Jim Baxter [mailto:jim...@uk...]
> >> Sent: Thursday, March 28, 2013 5:01 AM
> >> To: lin...@li...
> >> Subject: [Linuxptp-users] Validating PTP
> >>
> >> Is there a way to test the PTP time received by a ptp4l slave device?
> >>
> >> I am trying to test it is working correctly.
> >>
> >> Thank you for your help,
> >> Jim
> >>
> >>
> > It really depends on what you mean by this? You want to know
> whether the hardware timestamp is correct? Only way to reliably do
> that would be a bus analyzer I expect...
> >
> > You need to clarify what goal you are trying to achieve here..
> >
> > Thanks
> >
> > - Jake
> >
> Hi,
> 
> Perhaps I was misunderstanding PTP, I wanted to be able to use or view
> the timestamp so I know it is working correctly.
> 
> Can it be used by phc2sys to set the CLOCK_REALTIME?
> 
> Thanks,
> Jim

Yes. There is also available in the Documentation/ptp of the linux kernel which lets you run commands on any ptp device.

That is probably what you are looking for.

As for setting clock_realtime, you can do this via running "./phc2sys -i ethX" if you are running on kernel 3.5 or newer. Else you need to determine which /dev/ptpX device you are setting in ptp4l, and use "./phc2sys -d /dev/ptpX" 

That should begin tuning the CLOCK_REALTIME, which will set the kernel time to match that PPS, and keep it in track. You will probably want to disable the ntp/etc services that would conflict with this. Also note that you may not see a time update in something like a panel update for a little while. Those applets I have noticed taking a bit to update to the new time.

You can tweak the settings on this but the defaults should be alright.

It might be handy for someone to right daemon init scripts or systemd scripts, but I do not have time to do this at present.

Hope that information helps

Thanks

- Jake