diff options
| author | Ian Abbott <abbotti@mev.co.uk> | 2015-10-27 16:59:20 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-29 08:58:36 +0900 |
| commit | 4e5ffbf29c2042464c64998d2798431c358df251 (patch) | |
| tree | fe1cb489adf60dc7b63e84934016b9fd67f35cdf /drivers/staging/comedi | |
| parent | f3f24dff89748215f7f3054487731bec3b618669 (diff) | |
staging: comedi: comedi_test: make timer rate similar to scan rate
The asynchronous command handling for the analog input subdevice uses a
kernel timer which expires approximately `HZ` times a second. However,
it only needs to do anything after each scan period. Set the timer to
expire just after the next scan period.
Although the timer expiry function `waveform_ai_interrupt()` uses
precise time values to generate the fake waveforms used to generate the
data, those time values are constructed in a precise sequence, and do
not depend on the time the timer expiry function is actually called. So
the timer expiry rate does not have to be very precise.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging/comedi')
| -rw-r--r-- | drivers/staging/comedi/drivers/comedi_test.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c index 1b3ad7fb3720..9655dc333e34 100644 --- a/drivers/staging/comedi/drivers/comedi_test.c +++ b/drivers/staging/comedi/drivers/comedi_test.c @@ -52,6 +52,7 @@ #include <linux/timer.h> #include <linux/ktime.h> +#include <linux/jiffies.h> #define N_CHANS 8 @@ -215,10 +216,12 @@ static void waveform_ai_interrupt(unsigned long arg) if (devpriv->wf_current >= devpriv->wf_period) devpriv->wf_current %= devpriv->wf_period; - if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg) + if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg) { async->events |= COMEDI_CB_EOA; - else - mod_timer(&devpriv->ai_timer, jiffies + 1); + } else { + mod_timer(&devpriv->ai_timer, + jiffies + usecs_to_jiffies(devpriv->ai_scan_period)); + } comedi_handle_events(dev, s); } @@ -354,7 +357,9 @@ static int waveform_ai_cmd(struct comedi_device *dev, wf_current = devpriv->ai_last_scan_time; devpriv->wf_current = do_div(wf_current, devpriv->wf_period); - devpriv->ai_timer.expires = jiffies + 1; + devpriv->ai_timer.expires = + jiffies + usecs_to_jiffies(devpriv->ai_scan_period); + /* mark command as active */ smp_mb__before_atomic(); set_bit(WAVEFORM_AI_RUNNING, &devpriv->state_bits); |