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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 # PPS generators configuration
# #
if PPS
comment "PPS generators support" comment "PPS generators support"
config PPS_GENERATOR_PARPORT config PPS_GENERATOR_PARPORT
tristate "Parallel port PPS signal generator" tristate "Parallel port PPS signal generator"
depends on PARPORT != n && GENERIC_TIME depends on PARPORT
help help
If you say yes here you get support for a PPS signal generator which 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 utilizes STROBE pin of a parallel port to send PPS signals. It uses
parport abstraction layer and hrtimers to precisely control the signal. 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; long lim, delta;
unsigned long flags; unsigned long flags;
/* NB: approx time with blocked interrupts = /* We have to disable interrupts here. The idea is to prevent
send_delay + 3 * SAFETY_INTERVAL */ * 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); local_irq_save(flags);
/* first of all we get the time stamp... */ /* first of all we get the time stamp... */