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| author | Alexander Gordeev | 2011-01-13 02:01:00 +0100 |
|---|---|---|
| committer | Linus Torvalds | 2011-01-13 17:03:21 +0100 |
| commit | 563558b2c7350371551bf08348ac61be62200505 (patch) | |
| tree | e7f767bf68efd16a8784c8875d885ba6ea9ecf6d /drivers/pps/generators/pps_gen_parport.c | |
| parent | pps: add parallel port PPS signal generator (diff) | |
| download | kernel-qcow2-linux-563558b2c7350371551bf08348ac61be62200505.tar.gz kernel-qcow2-linux-563558b2c7350371551bf08348ac61be62200505.tar.xz kernel-qcow2-linux-563558b2c7350371551bf08348ac61be62200505.zip | |
pps: add parallel port PPS signal generator
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>
Diffstat (limited to 'drivers/pps/generators/pps_gen_parport.c')
| -rw-r--r-- | drivers/pps/generators/pps_gen_parport.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/pps/generators/pps_gen_parport.c b/drivers/pps/generators/pps_gen_parport.c index a15fe25efd55..5c32f8dacf56 100644 --- a/drivers/pps/generators/pps_gen_parport.c +++ b/drivers/pps/generators/pps_gen_parport.c @@ -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... */ |