]> git.karo-electronics.de Git - linux-beck.git/commit
ntp: add hardpps implementation
authorAlexander Gordeev <lasaine@lvk.cs.msu.su>
Thu, 13 Jan 2011 01:00:56 +0000 (17:00 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 13 Jan 2011 16:03:20 +0000 (08:03 -0800)
commit025b40abe715d638e60516a657d354e8560c1a85
tree9320d3993c65c4eb56d3ab30337d590eb8c892fd
parent12f9b1f9c11700893a7b453705d95b260d78f268
ntp: add hardpps implementation

This commit adds hardpps() implementation based upon the original one from
the NTPv4 reference kernel code from David Mills.  However, it is highly
optimized towards very fast syncronization and maximum stickness to PPS
signal.  The typical error is less then a microsecond.

To make it sync faster I had to throw away exponential phase filter so
that the full phase offset is corrected immediately.  Then I also had to
throw away median phase filter because it gives a bigger error itself if
used without exponential filter.

Maybe we will find an appropriate filtering scheme in the future but it's
not necessary if the signal quality is ok.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/pps/Kconfig
include/linux/timex.h
kernel/time/ntp.c