[LinuxPPS] kernel 2.6.32 - ntpd-4.2.6 linuxpps experiences

[clemens at dwf.com]

> Hello all, 
> 
> Having been an early LinuxPPS adaptor, it has been quiet for a while from this 
> side. 
> 
> Today I decided to upgrade my kernel from 2.6.27.6 to 2.6.32 and had to figure 
> out 'how on earth did I manage(d) to get LinuxPPS running after a kernel 
> upgrade?'.
> 
> After downloading kernel 2.6.32, I applied the ntp-pps-v2.6.32-rc8.diff patch, 
> compiled the kernel, and rebooted.
> 

<snip>

> 
> I discovered that the NANO option in timex.h is inserted as of kernel 2.6.30.
> However, for whatever reason with this timex.h ntpd failed to compile. So I 
> used the 'old' timex.h nano patch from the mid 2008s instead, which worked. 
> 

Yes the NANO defines FOR THE KERNEL are in the kernel version of timex.h
but these are STA_NANO and ADJ_NANO, ntpd needs MOD_NANO, and this is
*not* in the kernel version of this timex.h .

> I used ntpd-4.2.5-p113 and after starting the freshly compiled ntpd I could 
> not find my Oncore (driver 30) in the peers list (ntpq -p). 
> 

Not sure why, but that version is over a year old.
The ONCORE driver really hasnt had any changes.

> Having more things to do today than being busy with LinuxPPS I downloaded the 
> latest stable ntp version (4.2.6) and compiled it. 
> 
> With this version GPS_ONCORE(0) appeared in the peers list, but no 
> synchronization could be detected. 
> 
Again, I dont understand this.
I have been running with the 2.6.32 since it was released, and with various
of the prerelease versions of ntp with no problems.

> Knowing that I had PPS stamps, I tried the ATOM driver (driver 22), and used a 
> preferred time source from my local network. After a while ntpd-4.2.6 synced 
> to my PPS signal ... WITH the ppsfreq, and ppstime bits set (!). 
> 
> remco at helium > ntpdc -c kern
> pll offset:           -6.82e-07 s
> pll frequency:        17.942 ppm
> maximum error:        0.007736 s
> estimated error:      0 s
> status:               2007  pll ppsfreq ppstime nano
> pll time constant:    4
> precision:            1e-09 s
> frequency tolerance:  500 ppm
> 
> remco at helium > ntpq -p
>      remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> oPPS(0)          .PPS.            0 l   13   16  377    0.000   -0.001   0.002
> *freebsd         .GPS.            1 u   63   64  377    0.211    0.000   0.012
> +lithium         .DCFa.           1 u   42   64  377    0.157   -0.655   0.110
> +ptbtime1.ptb.de .PTB.            1 u   46   64  377   49.874    0.244   0.198
> 
> The stability seems to be better than with the 2001 status (pll , nano) but I 
> wonder why the Oncore driver fails to work. 
> 

Beats me, you are using the current kernel and a current version of ntpd,
which is the same as Im running.  Everything should 'just work'.


-- 
                                        Reg.Clemens
                                        reg at dwf.com