[LinuxPPS] Linuxpps on 2.6.28 vs. ntpd 4.2.4p6

[Thorsten Mühlfelder]

Hi Heiko

I've used kernel 2.6.28rc6 with ntp 4.2.4p5 for about 3 weeks without
problems on my test machines. Today I've done an upgrade to kernel
2.6.28 and ntp 4.2.4p6. With this combination the ntpd doesn't use the
PPS signal. I've checked ntpd syslog entries but there was nothing
special. So I've decided to play with the different versions and these
are my results:

2.6.28rc6 + 4.2.4p5 = working
2.6.28rc6 + 4.2.5p6 = not working
2.6.28 + 4.2.4p5 = working
2.6.28 + 4.2.5p6 = not working

ppstest works in every case and restarting ppsldisc and ntp doesn't
change anything.
So the problem must be the ntpd 4.2.5p6.

Greetings
Thorsten

PS: I'm usin Meinberg DCF and GPS cards as time and PPS source in
different servers, too. But as PPS just uses the atom driver I don't
think it's a Meinberg related problem.

On Wed, 14 Jan 2009 12:42:54 +0100
Heiko Gerstung <heiko.gerstung at meinberg.de> wrote:

> Hi everybody!
> 
> I am trying to prepare a new kernel for our series of NTP time server 
> appliances called LANTIME (see our website if you are interested) but I 
> have problems getting ntp-4.2.4p6 to work with my 2.6.28 kernel and the 
> rc6 linuxpps patch.
> 
> What already works is that if I start ppsldisc /dev/ttyS0 on a console, 
> I can see that assert and clear events are correctly recognized in 
> /sys/class/pps/pps/assert and clear and they represent the 200ms pulse 
> width we are using on our GPS receivers.
> 
> But for some it does not work when I start ppsldisc as a background 
> process during startup. I can see that there are a number of events 
> recorded because the assert file for example shows a timestamp and the 
> event count, which can be #32 for example or #43 but does not recognize 
> any further events until I "killall ppsldisc" and run ppsldisc on my 
> console (in the foreground).
> 
> Additionally, when I start ntpd, it cannot initialize the Atom driver 
> and the parse driver also cannot setup PPS usage:
> > Jan 14 09:17:19 LantimeV5 ntpd[13940]: PARSE receiver #0: parse_start: 
> > could not set up PPS: Invalid argument
> > Jan 14 09:17:19 LantimeV5 ntpd[13940]: PARSE receiver #0: 
> > parse_ppsapi: time_pps_getcap failed: Bad file descriptor
> > Jan 14 09:17:19 LantimeV5 ntpd[13940]: refclock_atom: time_pps_create 
> > failed: Inappropriate ioctl for device 
> I am not running udev on my machine and therefore have to create the 
> /dev/pps0 device node manually. I can see from /sys/class/pps/pps0/dev 
> that this should be c254:0 and therefore run "mknod /dev/pps0 c 254 0" 
> before doing anything else at startup.
> 
> What am I missing? First and foremost I would like to get ntpd to use 
> the PPS stuff, but if someone has any hints on why ppsldisc does not 
> work when it is sent into the background, I would be grateful for any 
> hints.
> 
> Best Regards,
>   Heiko
> 
> 
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