Re: [Linuxptp-users] About ptp4l sync completed time

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

From: Takahiro Shimizu [mailto:tsh...@gm...]
Sent: Friday, March 09, 2012 1:34 AM
To: Richard Cochran; lin...@li...
Subject: Re: [Linuxptp-users] About ptp4l sync completed time

Hello Richard,

Thank you for the reply.

No, it is not normal.

With hardware time stamping, you should get withn 0.1 usec in about
one or two minutes.

OK. I see. I will check the driver again.

Here is the result of ptp4l.
After 5 sec, master offset is decreasing gradually.
I doubt the part of adjust in the ptp driver now.

time (sec)       master offset (ns)        adj       path delay (ns)
1        60830880        0          5664
:
: <snip>
:
4420  -20       32758513        2964
4421  -54       32758473        2966

> 2. Can I speed up the time till sync completed?

The clock servo (in pi.c) has a PI controller, and its constants do
affect the convergence performance.

However, I think you have errors in the time stamps, or missing time
stamps.

HTH,
Richard
I see. I will check it too.

Thanks and Best regards,
Takahiro Shimizu

I would suggest looking into your clock rate adjustment function. This is where the driver should be tuning the frequency of the clock. It might be possible that you aren't adjusting it correctly.

However, I should note that with my testing, different values in the PI servo can have a fair impact on convergence times. You might play around with those and see what kind of impact it has. I don't think changing those alone will be enough but it might help you find the cause of the issue.