Re: [chrony-users] PPS time

[scs@xxxxxxxxxx (Steve Summit)]

Miroslav Lichvar wrote:
> On Mon, Jul 01, 2019 at 09:03:44AM -0700, Steve Summit wrote:
> > ...the implication here is that there may be other, non-gpsd PPS
> > refclocks I could be using instead of gpsd.  I feel like I should
> > have come across these already, but where can I read about them?
>
> The SHM refclock provided by gpsd is not a PPS refclock from the
> chronyd's point of view. The timestamps already have seconds.
> chronyd supports PPS refclocks using a /dev/pps* device directly.

If I'm understanding you correctly, then: If I want to use
"raw" PPS, I need to (a) configure chronyd with something like
"refclock PPS /dev/pps0" and (b) configure the Linux kernel so
that /dev/pps0 reflects my actual PPS input.

(I'm still a bit fuzzy on (b), but I guess it's the sort of thing
that https://www.kernel.org/doc/Documentation/pps/pps.txt is
talking about.)

Anyway, thanks for putting up with all my questions -- I think
I'm getting there.  (This has been more complicated for me
because we're using a nonstandard hardware configuration for our
GPS and PPS inputs which, I belatedly realize, is suboptimal.)

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