Kernel PPS processing

[Hal Murray]

http://users.megapathdsl.net/~hmurray/ntpsec/glypnod-pps-kernel.png

If you turn on flag3 for a PPS driver on a Linux system, you get this error 
message:
06-20T12:25:32 ntpd[988]: refclock_params: kernel PLL (hardpps, RFC 1589) not 
implemented

I poked around a bit.  Those options are in drivers/pps/Kconfig  Here is the 
key chunk:
config NTP_PPS
        bool "PPS kernel consumer support"
        depends on !NO_HZ
        help
          This option adds support for direct in-kernel time
          synchronization using an external PPS signal.

          It doesn't work on tickless systems at the moment.

So I pulled over the sources and built a kernel with NO_HZ turned off and 
NTP_PPS turned on.

The next project is to figure out why it works so much better, or rather why 
the normal ntpd can't do a lot better.



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