From 4e5ffbf29c2042464c64998d2798431c358df251 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Tue, 27 Oct 2015 16:59:20 +0000 Subject: [PATCH] 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 Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/comedi_test.c | 13 +++++++++---- 1 file 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 #include +#include #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);