linux/drivers/pps/Kconfig
Alexander Gordeev 025b40abe7 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>
2011-01-13 08:03:20 -08:00

45 lines
1.2 KiB
Plaintext

#
# PPS support configuration
#
menu "PPS support"
config PPS
tristate "PPS support"
depends on EXPERIMENTAL
---help---
PPS (Pulse Per Second) is a special pulse provided by some GPS
antennae. Userland can use it to get a high-precision time
reference.
Some antennae's PPS signals are connected with the CD (Carrier
Detect) pin of the serial line they use to communicate with the
host. In this case use the SERIAL_LINE client support.
Some antennae's PPS signals are connected with some special host
inputs so you have to enable the corresponding client support.
To compile this driver as a module, choose M here: the module
will be called pps_core.ko.
config PPS_DEBUG
bool "PPS debugging messages"
depends on PPS
help
Say Y here if you want the PPS support to produce a bunch of debug
messages to the system log. Select this if you are having a
problem with PPS support and want to see more of what is going on.
config NTP_PPS
bool "PPS kernel consumer support"
depends on PPS && !NO_HZ
help
This option adds support for direct in-kernel time
syncronization using an external PPS signal.
It doesn't work on tickless systems at the moment.
source drivers/pps/clients/Kconfig
endmenu