[Linuxptp-users] Software timestamping

[Jan D. <jan...@gm...>]

Hello,

I'm trying to use ptp4l (Version 1.7) on a Raspberry Pi. Unfortunately the
device's network interface does not support hardware timestamping.

$ ethtool -T eth0
Time stamping parameters for eth0:
Capabilities:
    software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
    software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
PTP Hardware Clock: none
Hardware Transmit Timestamp Modes: none
Hardware Receive Filter Modes: none

I thought I could use software timestamping in this case. Though executing
ptp4l with option -S I see the following output:

$ ./ptp4l -i eth0 -S -m
ptp4l[42.597]: interface 'eth0' does not support requested timestamping mode
failed to create a clock

Obviously my understanding of option -S or software timestamping is wrong.

What is the difference between options -S and -H? What hardware support is
needed for option -S? Is it a driver problem?

Thanks,
Jan