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staging: comedi: comedi_test: simplify time since last AI scan

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The private data structure `struct waveform_private` currently uses
member `last` to remember the time of the last timer interrupt, and the
member `usec_remainder` to keep track of how far into a simulated scan
the interrupt occurred.  Replace these with a single new member
`ai_last_scan_time` that records the time of the last scan.  This
simplifies the calculation of the number of scans to simulate in the
timer routine, `waveform_ai_interrupt()`.

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 16:59:17 +00:00 • committed by Greg Kroah-Hartman
parent 21ec1bf734
commit 66d4da800d
1 changed files with 10 additions and 17 deletions
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27
drivers/staging/comedi/drivers/comedi_test.c
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@ -62,11 +62,10 @@ enum waveform_state_bits {
/* Data unique to this driver */
struct waveform_private {
struct timer_list timer;
ktime_t last; /* time last timer interrupt occurred */
u64 ai_last_scan_time; /* time of last AI scan in usec */
unsigned int uvolt_amplitude; /* waveform amplitude in microvolts */
unsigned int usec_period; /* waveform period in microseconds */
unsigned int usec_current; /* current time (mod waveform period) */
unsigned long usec_remainder; /* usec since last scan */
unsigned long state_bits;
unsigned int scan_period; /* scan period in usec */
unsigned int convert_period; /* conversion period in usec */
@ -184,27 +183,19 @@ static void waveform_ai_interrupt(unsigned long arg)
struct comedi_async *async = s->async;
struct comedi_cmd *cmd = &async->cmd;
unsigned int i, j;
/* all times in microsec */
unsigned long elapsed_time;
unsigned int num_scans;
ktime_t now;
/* check command is still active */
if (!test_bit(WAVEFORM_AI_RUNNING, &devpriv->state_bits))
return;
now = ktime_get();
elapsed_time = ktime_to_us(ktime_sub(now, devpriv->last));
devpriv->last = now;
num_scans =
(devpriv->usec_remainder + elapsed_time) / devpriv->scan_period;
devpriv->usec_remainder =
(devpriv->usec_remainder + elapsed_time) % devpriv->scan_period;
elapsed_time = ktime_to_us(ktime_get()) - devpriv->ai_last_scan_time;
num_scans = elapsed_time / devpriv->scan_period;
num_scans = comedi_nscans_left(s, num_scans);
for (i = 0; i < num_scans; i++) {
unsigned long scan_remain_period = devpriv->scan_period;
unsigned int scan_remain_period = devpriv->scan_period;
for (j = 0; j < cmd->chanlist_len; j++) {
unsigned short sample;
@ -219,6 +210,7 @@ static void waveform_ai_interrupt(unsigned long arg)
scan_remain_period -= devpriv->convert_period;
}
devpriv->usec_current += scan_remain_period;
devpriv->ai_last_scan_time += devpriv->scan_period;
}
if (devpriv->usec_current >= devpriv->usec_period)
devpriv->usec_current %= devpriv->usec_period;
@ -337,6 +329,7 @@ static int waveform_ai_cmd(struct comedi_device *dev,
{
struct waveform_private *devpriv = dev->private;
struct comedi_cmd *cmd = &s->async->cmd;
u64 usec_current;
if (cmd->flags & CMDF_PRIORITY) {
dev_err(dev->class_dev,
@ -356,10 +349,10 @@ static int waveform_ai_cmd(struct comedi_device *dev,
devpriv->scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;
}
devpriv->last = ktime_get();
devpriv->usec_current =
((u32)ktime_to_us(devpriv->last)) % devpriv->usec_period;
devpriv->usec_remainder = 0;
devpriv->ai_last_scan_time = ktime_to_us(ktime_get());
/* Determine time within waveform period. */
usec_current = devpriv->ai_last_scan_time;
devpriv->usec_current = do_div(usec_current, devpriv->usec_period);
devpriv->timer.expires = jiffies + 1;
/* mark command as active */