Re: [Linuxptp-devel] [PATCH] PHC Index is invalid in phc2sys when ptp4l is in free_running mode.

[Arun S. <sa...@nv...>]

Didn’t realize that Maciek Machnikowski’s proposal for PTP Time of Day proposal is still pending. I have attached here for reference.

From: Miroslav Lichvar <mli...@re...>
Date: Wednesday, July 26, 2023 at 12:37 AM
To: Arun Saravanan <sa...@nv...>
Cc: Erez <ere...@gm...>, lin...@li... <lin...@li...>
Subject: Re: [Linuxptp-devel] [PATCH] PHC Index is invalid in phc2sys when ptp4l is in free_running mode.
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On Tue, Jul 25, 2023 at 06:12:50PM +0000, Arun Saravanan via Linuxptp-devel wrote:
> Use case is –
> ptp4l in free_running mode – PTP syncs the TOD
> PHC disciplined by other means, say PPS
> phc2sys source is PHC.

I'm sorry, I still don't follow.

What exactly is "PTP" and "TOD" here? Is the ptp4l's PTP port in
master or slave state? If former, why would you need
free_running_mode. If latter, what is the point of running ptp4l?

> With autocfg option phc2sys tries to get the phc_index from ptp4l to determine the source. But since ptp4l is free running mode, pmc_agent_query_port_properties will not give the phc_index.

> Ptp4l doesn’t know about PHC since it is not disciplining it.

Well, to me that would seem like the right thing to do. The PHC is not
synchronized, so phc2sys shouldn't be using it for synchronization of
other clocks.

--
Miroslav Lichvar