Re: [Linuxptp-users] Running ptp4l using UTC timescale with hardware time stamping

[Richard C. <ric...@gm...>]

On Tue, Feb 18, 2014 at 02:48:08PM +0000, Koehrer Mathias (ETAS/ESW5) wrote:
> Hi all,
> 
> we want to synchronize a couple of PCs. These PCs have to run for a couple of hours in a synchronized way.
> We do not have a proper grandmaster clock, one of the PCs plays this role.
> We use suitable Ethernet adapters (Intel IGB driver) to use the hardware time stamping.
> In this setup the usage of the separate PTP time scale (with the offset of 35s against UTC) is really confusing.
> Is it possible to force ptp4l to use UTC also for hardware time stamping e.g. by using an option (in the config file)?

I don't see an easy way to support this. Both the ptp4l and phc2sys
programs have code handling UTC-TAI conversion, but only for the
expected used cases. If you have a real PTP device, the assumption is
that you are also using the PTP timescale. We only use UTC when
absolutely required, for software time stamps.

You *could* try and hack this in, but I think it would be easier just
to maintain the PTP timescale in the PHC device.

Recent Linux kernels offer CLOCK_TAI, so you might consider using that
instead of CLOCK_REALTIME in your application.

Sorry,
Richard