[Linuxptp-users] ntpd synchronization issue to ptp source

[Jakub R. <j.r...@el...>]

Greetings,

I would like to ask a question/report an issue.
Our setup: PTP Master & Slave based on imx6ul module, connected via simple switch. We set ptp4l to synchronize ntpd.

Issue:
When we synchronize PTP device to Master and then disconnect ethernet cable from PTP Slave (from device, not from switch), the PTP Slave device changes portState to 'Faulty' and time gets stuck, but still synchronized ntpd.

So first question - I checked linuxptp source and it seems that once PTP has ever synchronized, it will always synchronize ntpd, whether linuxptp is connected to Master device or is in holdover. Is it indented behavior? Is it targeted for custom PTP devices that have much better holdover than ntpd could ever have?

Second question - is this bug caused by ethernet driver or is it linuxptp issue? I am not asking to check imx6ul driver but rather answer whether it should have been prevented by linuxptp. 
It is related to first question a bit, as it would not happen if linuxptp marked 'Faulty' Master as invalid ntpd source.

Attaching log and explanation - i used command 'watch' to log PTP and ntpd state before/during/after ethernet cable was disconnected. When cable is disconnected portState switches to 'Faulty' and time gets stuck; it gets unstuck when cable in reconnected (all included in log file)

Thanks for the help.

Best regards
Jakub Raczynski