[Linuxptp-users] Switching PHC when link goes down and up again

[Osterried M. (ETAS-DAP/XPC-Fe3) <mar...@et...>]

Hi,

I have built from latest linuxptp snapshot, because I want to use the virtual clock support.

I have created two virtual clocks (/dev/ptp2 and /dev/ptp3), based on the physical clock /dev/ptp1:
echo 2 >/sys/class/ptp/ptp1/n_vclocks

Then I have started ptp4l with this command line:
./ptp4l -i swp0 --phc_index=2 -m

This is an extract of the messages when ptp4l starts, then link goes down and link goes up again:
ptp4l[10842.853]: selected /dev/ptp2 as PTP clock
ptp4l[10842.854]: port 1 (swp0): /dev/ptp2 is virtual clock
ptp4l[10864.838]: port 1 (swp0): link down
ptp4l[10878.197]: port 1 (swp0): link up
ptp4l[10878.202]: Switching PHC, failed to open /dev/ptp1: Device or resource busy

It seems when link goes up ptp4l wants to switch from requested /dev/ptp2 to physical clock /dev/ptp1, which fails.
Why does ptp4l switch the PHC when link is changed?

I think the given command line is the preferred one, but the behavior is the same with this command line:
./ptp4l -i swp0 -p /dev/ptp2 -m


Regards
Markus