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>
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>
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>
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>
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>
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>
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>
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>
