[Linuxptp-users] LinuxPTP Software Timestamping only - PHC Concept

[Jean-Sebastien S. <js....@gm...>]

Hello,

I am running linuxPTP 1.8 on a 4.14.0-xilinx device.

This device only has software timestamping made available.









*root@Megalive:~# ethtool -T eth0Time stamping parameters for
eth0:Capabilities:        software-transmit
(SOF_TIMESTAMPING_TX_SOFTWARE)        software-receive
 (SOF_TIMESTAMPING_RX_SOFTWARE)        software-system-clock
(SOF_TIMESTAMPING_SOFTWARE)PTP Hardware Clock: noneHardware Transmit
Timestamp Modes: noneHardware Receive Filter*

I'm able to synchronize this device running as a TimeReceiver, to a
TimeSender, at least reportedly. ptp4l will report that the servo S2 state
is reached and stable, with a reported offset to the TimeSender in the 1us
range (with occasional jumps to double digit offsets).
I am ok with this offset jitter, provided it is reported in an accurate way.

When it comes to software timestamping, what is the PHC equivalent on the
device? Is it a hardware timer? Or is it purely software? ethtool is
reporting no PHC, and so I'd assume the PHC is some sort of software timer
somewhere in the kernel.
Can a virtual PPS be generated from this virtual PHC, in the form of an
event potentially? How would you handle this event?

Regards,
JS