diff options
| author | Ian Abbott <abbotti@mev.co.uk> | 2017-06-30 12:02:18 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-07-27 15:08:06 -0700 |
| commit | 2bc52403da8a940d3ecc1b4c770cab9a650167ae (patch) | |
| tree | a3a01199d0b295528e8e4c37f03e42db96a023fa /drivers | |
| parent | 964a21a1300c2857483e85f1d013c5867ee4d433 (diff) | |
staging: comedi: ni_mio_common: fix AO timer off-by-one regression
commit 15d5193104a457d5151840247e3bce561c42e3e9 upstream.
As reported by Éric Piel on the Comedi mailing list (see
<https://groups.google.com/forum/#!topic/comedi_list/ueZiR7vTLOU/discussion>),
the analog output asynchronous commands are running too fast with a
period 50 ns shorter than it should be. This affects all boards with AO
command support that are supported by the "ni_pcimio", "ni_atmio", and
"ni_mio_cs" drivers.
This is a regression bug introduced by commit 080e6795cba3 ("staging:
comedi: ni_mio_common: Cleans up/clarifies ni_ao_cmd"), specifically,
this line in `ni_ao_cmd_set_update()`:
/* following line: N-1 per STC */
ni_stc_writel(dev, trigvar - 1, NISTC_AO_UI_LOADA_REG);
The `trigvar` variable value comes from a call to `ni_ns_to_timer()`
which converts a timer period in nanoseconds to a hardware divisor
value. The function already reduces the divisor by 1 as required by the
hardware, so the above line should not reduce it further by 1. Fix it
by replacing `trigvar` by `trigvar - 1` in the above line, and remove
the misleading comment.
Reported-by: Éric Piel <piel@delmic.com>
Fixes: 080e6795cba3 ("staging: comedi: ni_mio_common: Cleans up/clarifies ni_ao_cmd")
Cc: Éric Piel <piel@delmic.com>
Cc: Spencer E. Olson <olsonse@umich.edu>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/staging/comedi/drivers/ni_mio_common.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c index 1c967c30e4ce..a574885ffba9 100644 --- a/drivers/staging/comedi/drivers/ni_mio_common.c +++ b/drivers/staging/comedi/drivers/ni_mio_common.c @@ -3078,8 +3078,7 @@ static void ni_ao_cmd_set_update(struct comedi_device *dev, /* following line: 2-1 per STC */ ni_stc_writel(dev, 1, NISTC_AO_UI_LOADA_REG); ni_stc_writew(dev, NISTC_AO_CMD1_UI_LOAD, NISTC_AO_CMD1_REG); - /* following line: N-1 per STC */ - ni_stc_writel(dev, trigvar - 1, NISTC_AO_UI_LOADA_REG); + ni_stc_writel(dev, trigvar, NISTC_AO_UI_LOADA_REG); } else { /* TRIG_EXT */ /* FIXME: assert scan_begin_arg != 0, ret failure otherwise */ devpriv->ao_cmd2 |= NISTC_AO_CMD2_BC_GATE_ENA; |