On 2014-02-28 23:24, H Hartley Sweeten wrote:
The interrupt is only generated by the hardware at the completion of
an A/D conversion. Because of this the sanity check to make sure that
the A/D conversion is complete and data is available is probably
unnecessary but it doesn't hurt anything.
The busywait loop is a different issue. Interrupt routines should not
busywait. That's just mean...
Remove the bustwait and use pcl816_ai_eoc() to check for the end-of-
conversion.
Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com>
Cc: Ian Abbott <abbo...@mev.co.uk>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/staging/comedi/drivers/pcl816.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/drivers/staging/comedi/drivers/pcl816.c
b/drivers/staging/comedi/drivers/pcl816.c
index 66d3c5a..6000ca91 100644
--- a/drivers/staging/comedi/drivers/pcl816.c
+++ b/drivers/staging/comedi/drivers/pcl816.c
@@ -279,22 +279,14 @@ static irqreturn_t interrupt_pcl816_ai_mode13_int(int
irq, void *d)
struct pcl816_private *devpriv = dev->private;
struct comedi_subdevice *s = dev->read_subdev;
struct comedi_cmd *cmd = &s->async->cmd;
- int timeout = 50; /* wait max 50us */
- while (timeout--) {
- if (!(inb(dev->iobase + PCL816_STATUS) &
- PCL816_STATUS_DRDY_MASK))
- break;
- udelay(1);
- }
- if (!timeout) { /* timeout, bail error */
+ if (pcl816_ai_eoc(dev, s, NULL, 0)) {
outb(0, dev->iobase + PCL816_CLRINT); /* clear INT
request */
comedi_error(dev, "A/D mode1/3 IRQ without DRDY!");
s->cancel(dev, s);
s->async->events |= COMEDI_CB_EOA | COMEDI_CB_ERROR;
comedi_event(dev, s);
return IRQ_HANDLED;
-
}
comedi_buf_put(s->async, pcl816_ai_get_sample(dev, s));
Curiously, the user manual for this card suggests the interrupt occurs
at the start of the conversion, rather than the end. On page 42 of the
user manual:
5.7. A/D Data Transfer
[snip]
2. Interrupt Routine
[...] At the start of each conversion, the A/D Trigger signal
generates an interrupt that enables the interrupt service routine to
perform the transfer. [...]
So it seems the interrupt routine needs to wait for the DRDY bit to be
set, at least for this transfer mode, which isn't actually used by the
driver! I think this mode was disabled for reliability reasons in the
dim and distant past, although it seems it was only half-disabled;
pcl816_ai_cmd() only uses the DMA modes, but command support is enabled
in pcl816_attach() even if the DMA channel has not been configured (it
shouldn't be allowed unless both the IRQ and DMA channel have been
configured).
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbo...@mev.co.uk> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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