linux-toradex.git/drivers/pps, branch v2.6.38-rc2

pps: add parallel port PPS signal generator

2011-01-13T16:03:21+00:00

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 
Cc: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: add parallel port PPS signal generator

2011-01-13T16:03:21+00:00

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 
Acked-by: Rodolfo Giometti 
Cc: john stultz 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: add parallel port PPS client

2011-01-13T16:03:21+00:00

Add parallel port PPS client.  It uses a standard method for capturing
timestamps for assert edge transitions: getting a timestamp soon after an
interrupt has happened.

This is not a very precise source of time information due to interrupt
handling delays.  However, timestamps for clear edge transitions are much
more precise because the interrupt handler continuously polls hardware
port until the transition is done.

Hardware port operations require only about 1us so the maximum error
should not exceed this value.  This was my primary goal when developing
this client.

Clear edge capture could be disabled using clear_wait parameter.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: add kernel consumer support

2011-01-13T16:03:21+00:00

Add an optional feature of PPSAPI, kernel consumer support, which uses the
added hardpps() function.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ntp: add hardpps implementation

2011-01-13T16:03:20+00:00

This commit adds hardpps() implementation based upon the original one from
the NTPv4 reference kernel code from David Mills.  However, it is highly
optimized towards very fast syncronization and maximum stickness to PPS
signal.  The typical error is less then a microsecond.

To make it sync faster I had to throw away exponential phase filter so
that the full phase offset is corrected immediately.  Then I also had to
throw away median phase filter because it gives a bigger error itself if
used without exponential filter.

Maybe we will find an appropriate filtering scheme in the future but it's
not necessary if the signal quality is ok.

Signed-off-by: Alexander Gordeev 
Acked-by: John Stultz 
Cc: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: timestamp is always passed to dcd_change()

2011-01-13T16:03:20+00:00

Remove the code that gatheres timestamp in pps_tty_dcd_change() in case
passed ts parameter is NULL because it never happens in the current code.
Fix comments as well.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: simplify conditions a bit

2011-01-13T16:03:20+00:00

Bitwise conjunction is distributive so we can simplify some conditions.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: use BUG_ON for kernel API safety checks

2011-01-13T16:03:20+00:00

This way less overhead is involved when running production kernel.  If you
want to debug a pps client module please define DEBUG to enable the
checks.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: make idr lock a mutex and protect idr_pre_get

2011-01-13T16:03:20+00:00

Now pps_idr_lock is never used in interrupt context so we can replace
spin_lock_irq/spin_unlock_irq with plain spin_lock/spin_unlock. But
there is also a potential race condition when someone can steal an id
which was allocated by idr_pre_get before it is used. So convert spin
lock to mutex and protect the whole id generation process.

Signed-off-by: Alexander Gordeev 
Cc: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: move idr stuff to pps.c

2011-01-13T16:03:20+00:00

Since now idr is only used to manage char device id's and not used in
kernel API anymore it should be moved to pps.c.  This also makes it
possible to release id only at actual device freeing so nobody can
register a pps device with the same id while our device is not freed yet.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds