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staging: comedi: comedi_test: move modulo operations for waveform

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The fake waveform generator functions, `fake_sawtooth()` and
`fake_squarewave()`, called from `fake_waveform()`, have a
`current_time` parameter which is the time since the start of a waveform
period.  The parameter value may be greater than the waveform period so
they do a modulo operation to bring it into range.  Do the modulo
operations outside the functions in `waveform_ai_interrupt()` so that
the waveform generator functions always get a `current_time` parameter
less than the waveform period and do not have to do the modulo operation
themselves.  Also, only do the modulo operations when the time since the
start of a waveform exceeds the waveform period.  Usually, several
samples are produced in each waveform period and modulo operations are
typically more expensive than a simple comparison.

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>
This commit is contained in:
Ian Abbott 2015-10-27 16:59:15 +00:00 committed by Greg Kroah-Hartman
parent 783ddaebd3
commit 8fa8a260d2
1 changed files with 10 additions and 8 deletions
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18
drivers/staging/comedi/drivers/comedi_test.c
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@ -97,7 +97,6 @@ static unsigned short fake_sawtooth(struct comedi_device *dev,
binary_amplitude *= devpriv->uvolt_amplitude;
do_div(binary_amplitude, krange->max - krange->min);
current_time %= devpriv->usec_period;
value = current_time;
value *= binary_amplitude * 2;
do_div(value, devpriv->usec_period);
@ -125,7 +124,6 @@ static unsigned short fake_squarewave(struct comedi_device *dev,
const struct comedi_krange *krange =
&s->range_table->range[range_index];
current_time %= devpriv->usec_period;
value = s->maxdata;
value *= devpriv->uvolt_amplitude;
do_div(value, krange->max - krange->min);
@ -206,20 +204,24 @@ static void waveform_ai_interrupt(unsigned long arg)
num_scans = comedi_nscans_left(s, num_scans);
for (i = 0; i < num_scans; i++) {
unsigned long scan_remain_period = devpriv->scan_period;
for (j = 0; j < cmd->chanlist_len; j++) {
unsigned short sample;
if (devpriv->usec_current >= devpriv->usec_period)
devpriv->usec_current %= devpriv->usec_period;
sample = fake_waveform(dev, CR_CHAN(cmd->chanlist[j]),
CR_RANGE(cmd->chanlist[j]),
devpriv->usec_current +
i * devpriv->scan_period +
j * devpriv->convert_period);
devpriv->usec_current);
comedi_buf_write_samples(s, &sample, 1);
devpriv->usec_current += devpriv->convert_period;
scan_remain_period -= devpriv->convert_period;
}
devpriv->usec_current += scan_remain_period;
}
devpriv->usec_current += elapsed_time;
devpriv->usec_current %= devpriv->usec_period;
if (devpriv->usec_current >= devpriv->usec_period)
devpriv->usec_current %= devpriv->usec_period;
if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg)
async->events |= COMEDI_CB_EOA;