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2017-01-05Doc: clarify source of jitter in USB1.1, and USB2.0Sanjeev1-2/+5
Even though the jitter due to USB1.1 may be 1ms, NTP can reduce its effect significantly. And USB2.0 reduces this anyway. Signed-off-by: Sanjeev Gupta <ghane0@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-01-05Doc: Typos in documentationSanjeev1-2/+2
No semantic changes. The next patch in this series will do the actual changes to sync with NTP current best practices Signed-off-by: Sanjeev Gupta <ghane0@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-01-05Doc: Correct PPS doc to reflect code locationSanjeev1-3/+4
timepps.h , as well as PPS sample test utilities, are no longer in the kernel tree. Update documentation to point to new locations. Signed-off-by: Sanjeev Gupta <ghane0@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2016-04-28Documentation: pps: fix spelling mistakeEric Engestrom1-1/+1
Signed-off-by: Eric Engestrom <eric@engestrom.ch> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2015-07-14Doc: pps: Fix file name in pps.txtMasanari Iida1-1/+1
This patch fix a file name of example code. Signed-off-by: Masanari Iida <standby24x7@gmail.com> Acked-by: Rodolfo Giometti <giometti@enneenne.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2015-06-22Doc:pps: Fix typo in pps.txtMasanari Iida1-1/+1
This patch fix a spelling typo in Documentation/pps/pps.txt Signed-off-by: Masanari Iida <standby24x7@gmail.com> Acked-by: Rodolfo Giometti <giometti@enneenne.com> [jc: did s/into/in the/ on the same line while we were there] Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2013-09-26USB: serial: invoke dcd_change ldisc's handler.Paul Chavent1-0/+15
The DCD pin of the serial port can receive a PPS signal. By calling the port line discipline dcd handle, this patch allow to monitor PPS through USB serial devices. However the performance aren't as good as the uart drivers, so document this point too. Signed-off-by: Paul Chavent <paul.chavent@onera.fr> Acked-by: Rodolfo Giometti <giometti@enneenne.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2011-01-13pps: add parallel port PPS signal generatorAlexander Gordeev1-0/+46
Add PPS signal generator which utilizes STROBE pin of a parallel port to send PPS signals. It uses parport abstraction layer and hrtimers to precisely control the signal. [akpm@linux-foundation.org: fix build] Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su> Acked-by: Rodolfo Giometti <giometti@linux.it> Cc: john stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-19LinuxPPS: core supportRodolfo Giometti1-0/+172
This patch adds the kernel side of the PPS support currently named "LinuxPPS". PPS means "pulse per second" and a PPS source is just a device which provides a high precision signal each second so that an application can use it to adjust system clock time. Common use is the combination of the NTPD as userland program with a GPS receiver as PPS source to obtain a wallclock-time with sub-millisecond synchronisation to UTC. To obtain this goal the userland programs shoud use the PPS API specification (RFC 2783 - Pulse-Per-Second API for UNIX-like Operating Systems, Version 1.0) which in part is implemented by this patch. It provides a set of chars devices, one per PPS source, which can be used to get the time signal. The RFC's functions can be implemented by accessing to these char devices. Signed-off-by: Rodolfo Giometti <giometti@linux.it> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg KH <greg@kroah.com> Cc: Randy Dunlap <randy.dunlap@oracle.com> Cc: Kay Sievers <kay.sievers@vrfy.org> Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>