From 025b40abe715d638e60516a657d354e8560c1a85 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Wed, 12 Jan 2011 17:00:56 -0800 Subject: 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 Acked-by: John Stultz Cc: Rodolfo Giometti Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/pps/Kconfig | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/pps') diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig index 1afe4e03440..0ad5ff38bfe 100644 --- a/drivers/pps/Kconfig +++ b/drivers/pps/Kconfig @@ -30,6 +30,15 @@ config PPS_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 -- cgit v1.2.3