Re: [Linuxptp-users] Master offsets don't converge

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

On Fri, 2016-01-15 at 16:19 +0000, Daniel Le wrote:
> Hello,
>  
> My ptp4l version 1.4 in software timestamping mode works fine with a
> Linux kernel 2.6.35, however when I switch to the kernel 3.18.12 (and
> new Ethernet driver), I see the master offsets are huge and never
> converge. Any pointer to debug this is much appreciated.
>  

You say this is software timestamping? What's your configuration? I
would suspect such a large kernel change to possibly be result of a
driver bug, but this wouldn't be the case if you're using pure software
timestamping. Can you copy your ptp4l.conf file?


Are you using only unmodified upstream versions? If you're using any
modifications, I would bisect through those, confirming that the
vanilla versions work just fine.

Regards,
Jake

> / #ptp4l -f /etc/ptp4l.conf
> ptp4l[250704.924]: port 1: INITIALIZING to LISTENING on INITIALIZE
> ptp4l[250704.924]: port 0: INITIALIZING to LISTENING on INITIALIZE
> ptp4l[250705.355]: port 1: new foreign master 00b0ae.fffe.02d103-1
> ptp4l[250708.955]: selected best master clock 00b0ae.fffe.02d103
> ptp4l[250708.955]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
> ptp4l[250709.856]: port 1: minimum delay request interval 2^-7
> ptp4l[250710.698]: master offset1 -6601404463576 s0 freq +100000000 path delay    220834
> ptp4l[250711.598]: master offset1 -6601404940762 s0 freq +100000000 path delay    224676
> ptp4l[250712.498]: master offset1 -6601405412898 s0 freq +100000000 path delay    223500 

This smells of a driver bug. Notice how the frequency shift is maxed,
and yet the clock is still drifting farther apart. This either means
that the real clock drift is *over* 10%, (which is very unlikely), or
there is a bug in the frequency tuning. But if you really are using
software timestamps, this doesn't make sense.


Again, if you're not using vanilla LinuxPTP 1.4, I would retry with
that and confirm the behavior. If you are using vanilla LinuxPTP, I
would confirm that you are infact actually using software only
timestamping.

Regards,
Jake