Yo Jacob E!
On Mon, 23 Feb 2015 21:09:01 +0000
"Keller, Jacob E" <jacob.e.kel...@intel.com> wrote:
> > Ouch... But I guess pure theory until a WiFi driver has real
> > support.
> >
>
> NTP and PTP are generally considered solutions to different but
> related problems, so this shouldn't really be an issue.
As a gpsd maintainer and longtime chronyd/ntpd user I 100% disagree!
Not having chronyd or ntpd in the loop is a total non-starter for me.
> > Odd, so automatic configuration not so automatic. I told ptp4l to
> > use ntpshm, that should be passed along.
> >
>
> ptp4l in hardware timestamp mode controls a hardware clock, which is
> completely unrelated to the system time clock.
Understood.
> Then, phc2sys controls
> the system clock based on the hardware clock which is set by ptp4l
Gack, maybe that is one way, but not a good way. Certainly not the
only way.
Since ptp4l can control the ntpshm in software timestamping mode why
can it not do so in hardware timestamping mode? Does ptp4l in hardware
mode ignore ntpsm in hardware mode, or does it continue to post parallel
software mode timing?
> This is sort of the flow.
>
> network -> ptp4l -> NIC hardware clock -> phc2sys -> system clock
So how do I get ntpshm in there?
And not valid for a local PPS based PTP master, maybe mmore like:
PPS -> ntpd -> local sysclock -> ptp4l -> NIC hardware clock -> phc2sys ->
ntpshm
And it has to be a loop, so when PPS is lost that host can feed the hardware
clock back into ntpd.
> Telling ptp4l to use the ntpshm doesn't work unless ptp4l is in
> software mode because ptp4l doesn't control teh software clock in
> hardware timestamp mode.
Weird. Why are not ptp4l and phc2sys one program? They are certainly
deeply intertwined. And ptp4l in software mode already does most of what
phc2sys does in hardware mode.
> > kong ~ # phc2sys -a -r -i eth0 -m -q
> > '-i' has been deprecated. please use '-s' instead.
> > autoconfiguration cannot be mixed with manual config options.
> Yea, I think you just need to drop the -i eth0 part.
With no -i phc2sys complains it has not port to connect to
And not replace with the -s? A bug in the error message?
> > Which will not start for me:
> >
> > kong ~ # ptp4l
> > no interface specified
>
>
> ptp4l does not by default look up any configuration file.
Understood. Another reason why I have only been runnning in default
mode when asked to do that, to prove that default mode does not work.
> default.cfg
> is provided to show the default settings. You must specify the
> configuration file via "-f" option.
Yup, if you look at my incomplete HOWTO you see I do that:
http://www.catb.org/gpsd/gpsd-time-service-howto.html
> > But this works:
> >
> > kong ~ # ptp4l -i eth0 &
> This won't do what you think because you didn't actually provide the
> configuration file.
Clearly it is non-functional. But it does what I was asked to try and
proved it does not work in any rational manner.
> > > I admit the options for phc2sys are really confusing. On the one
> > > hand, the phc2sys underwent a "organic" development process, and
> > > on the other hand, there really are a great many ways to
> > > configure the system clock and one (or more!) PTP hardware
> > > clocks. I always have to re-read the man page every time.
> >
>
> I am (slowly) working on updating the configuration code for all our
> utilities which should help alleviate some of these issues.
I look forward to that, but I've been told this can work as it exists
now. Not found any way to make hardware mode work (with ntpshm) yet.
> > And another cesspool is pmc. I see it makes a nice low level tool,
> > but time for a simple way to use it like 'pmc -a' and 'pmc -A'
> > which would dump all possible data in short and long form, like
> > 'hdparm -i' and 'hdparm -I' do for disks.
> >
>
> pmc is used to directly talk the management protocol specified by the
> PTP standard. I don't know if pmc -a or pmc -A make sense.
Why not? hdparm implements the SATA spec at low and high levels. Ditto
sdparm for SCSI and stty for RS-232.
This stuff needs to be de-mystified and automated if real users are
going to use it. RedHat has 10 pages of HOWTO and they still don't
get it right.
RGDS
GARY
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