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pps: add parallel port PPS signal generator

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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.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexander Gordeev 2011-01-12 17:01:00 -08:00 committed by Linus Torvalds
parent 46b402a0e5
commit 563558b2c7
2 changed files with 10 additions and 7 deletions
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6
drivers/pps/generators/Kconfig
View File

@ -2,16 +2,12 @@
# PPS generators configuration
#
if PPS
comment "PPS generators support"
config PPS_GENERATOR_PARPORT
tristate "Parallel port PPS signal generator"
depends on PARPORT != n && GENERIC_TIME
depends on PARPORT
help
If you say yes here you get support for a 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.
endif

11
drivers/pps/generators/pps_gen_parport.c
View File

@ -76,8 +76,15 @@ static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
long lim, delta;
unsigned long flags;
/* NB: approx time with blocked interrupts =
send_delay + 3 * SAFETY_INTERVAL */
/* We have to disable interrupts here. The idea is to prevent
* other interrupts on the same processor to introduce random
* lags while polling the clock. getnstimeofday() takes <1us on
* most machines while other interrupt handlers can take much
* more potentially.
*
* NB: approx time with blocked interrupts =
* send_delay + 3 * SAFETY_INTERVAL
*/
local_irq_save(flags);
/* first of all we get the time stamp... */