Currently this driver alwasy programs the DMA transfer to be the allocated
size of the DMA buffer. When the async command 'stop_src' is TRIG_COUNT its
possible (likely) for the last transfer to be less than the buffer size.
Introduce a helper function, das16_ai_setup_dma(), to calculate the actual
size of the DMA transfer based on the number of samples remaining and the
number of unread samples.
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/das16.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/drivers/staging/comedi/drivers/das16.c
b/drivers/staging/comedi/drivers/das16.c
index 3a2a6cc..86e90d5 100644
--- a/drivers/staging/comedi/drivers/das16.c
+++ b/drivers/staging/comedi/drivers/das16.c
@@ -448,6 +448,28 @@ struct das16_private_struct {
unsigned int timer_running:1;
};
+static void das16_ai_setup_dma(struct comedi_device *dev,
+ struct comedi_subdevice *s,
+ unsigned int unread_samples)
+{
+ struct das16_private_struct *devpriv = dev->private;
+ struct comedi_isadma *dma = devpriv->dma;
+ struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
+ unsigned int max_samples = comedi_bytes_to_samples(s, desc->maxsize);
+ unsigned int nsamples;
+
+ /*
+ * Determine dma size based on the buffer size plus the number of
+ * unread samples and the number of samples remaining in the command.
+ */
+ nsamples = comedi_nsamples_left(s, max_samples + unread_samples);
+ if (nsamples > unread_samples) {
+ nsamples -= unread_samples;
+ desc->size = comedi_samples_to_bytes(s, nsamples);
+ comedi_isadma_program(desc);
+ }
+}
+
static void das16_interrupt(struct comedi_device *dev)
{
struct das16_private_struct *devpriv = dev->private;
@@ -486,13 +508,9 @@ static void das16_interrupt(struct comedi_device *dev)
nsamples = comedi_bytes_to_samples(s, nbytes);
/* restart DMA if more samples are needed */
- if (nsamples && nsamples < comedi_nsamples_left(s, nsamples + 1)) {
- struct comedi_isadma_desc *nxt_desc;
-
+ if (nsamples) {
dma->cur_dma = 1 - dma->cur_dma;
- nxt_desc = &dma->desc[dma->cur_dma];
- nxt_desc->size = nxt_desc->maxsize;
- comedi_isadma_program(nxt_desc);
+ das16_ai_setup_dma(dev, s, nsamples);
}
spin_unlock_irqrestore(&dev->spinlock, spin_flags);
@@ -672,7 +690,6 @@ static int das16_cmd_exec(struct comedi_device *dev, struct
comedi_subdevice *s)
const struct das16_board *board = dev->board_ptr;
struct das16_private_struct *devpriv = dev->private;
struct comedi_isadma *dma = devpriv->dma;
- struct comedi_isadma_desc *desc = &dma->desc[0];
struct comedi_async *async = s->async;
struct comedi_cmd *cmd = &async->cmd;
unsigned int byte;
@@ -721,8 +738,7 @@ static int das16_cmd_exec(struct comedi_device *dev, struct
comedi_subdevice *s)
/* set up dma transfer */
dma->cur_dma = 0;
- desc->size = desc->maxsize;
- comedi_isadma_program(desc);
+ das16_ai_setup_dma(dev, s, 0);
/* set up timer */
spin_lock_irqsave(&dev->spinlock, flags);
--
2.0.3
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