Commit Graph

8 Commits

Author SHA1 Message Date
George Spelvin
513b032c98 pps: Add pps_lookup_dev() function
The PPS serial line discipline wants to attach a PPS device to a tty
without changing the tty code to add a struct pps_device * pointer.

Since the number of PPS devices in a typical system is generally very low
(n=1 is by far the most common), it's practical to search the entire list
of allocated pps devices.  (We capture the timestamp before the lookup,
so the timing isn't affected.)

It is a bit ugly that this function, which is part of the in-kernel
PPS API, has to be in pps.c as opposed to kapi,c, but that's not
something that affects users.

Signed-off-by: George Spelvin <linux@horizon.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-02-13 09:40:35 -08:00
Ben Hutchings
220a60a425 pps/ptp: Allow PHC devices to adjust PPS events for known delay
Initial version by Stuart Hodgson <smhodgson@solarflare.com>

Some PHC device drivers may deliver PPS events with a significant
and variable delay, but still be able to measure precisely what
that delay is.

Add a pps_sub_ts() function for subtracting a delay from the
timestamp(s) in a PPS event, and a PTP event type (PTP_CLOCK_PPSUSR)
for which the caller provides a complete PPS event.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
2012-09-07 21:13:28 +01:00
Alexander Gordeev
e2c18e49a0 pps: capture MONOTONIC_RAW timestamps as well
MONOTONIC_RAW clock timestamps are ideally suited for frequency
calculation and also fit well into the original NTP hardpps design.  Now
phase and frequency can be adjusted separately: the former based on
REALTIME clock and the latter based on MONOTONIC_RAW clock.

A new function getnstime_raw_and_real is added to timekeeping subsystem to
capture both timestamps at the same time and atomically.

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 08:03:21 -08:00
Alexander Gordeev
5e196d34a7 pps: access pps device by direct pointer
Using device index as a pointer needs some unnecessary work to be done
every time the pointer is needed (in irq handler for example).  Using a
direct pointer is much more easy (and safe as well).

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-13 08:03:19 -08:00
Alexander Gordeev
6f4229b511 pps: unify timestamp gathering
Add a helper function to gather timestamps.  This way clients don't have
to duplicate it.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-13 08:03:19 -08:00
Alexander Gordeev
3003d55b59 pps: fix race in PPS_FETCH handler
There was a race in PPS_FETCH ioctl handler when several processes want to
obtain PPS data simultaneously using sleeping PPS_FETCH.  They all sleep
most of the time in the system call.

With the old approach when the first process waiting on the pps queue is
waken up it makes new system call right away and zeroes pps->go.  So other
processes continue to sleep.  This is a clear race condition because of
the global 'go' variable.

With the new approach pps->last_ev holds some value increasing at each PPS
event.  PPS_FETCH ioctl handler saves current value to the local variable
at the very beginning so it can safely check that there is a new event by
just comparing both variables.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-13 08:03:19 -08:00
Alexander Gordeev
7a21a3cc0b pps: trivial fixes
Here are some very trivial fixes combined:

- add macro definitions to protect header file from including several times

- remove declaration for an unexistent array

- fix typos

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-13 08:03:19 -08:00
Rodolfo Giometti
eae9d2ba0c LinuxPPS: core support
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>
2009-06-18 13:04:04 -07:00