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@xxxxxxxxx>
---
drivers/staging/comedi/drivers/comedi_test.c | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)
diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index 158e090..78fde3a 100644
--- a/drivers/staging/comedi/drivers/comedi_test.c
+++ b/drivers/staging/comedi/drivers/comedi_test.c
@@ -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 */
--
2.6.1
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