The DMA operations used by the driver may have been set up to acquire
data from unwanted channels in addition to the wanted channels.
Currently, `interrupt_pci9118_ai_dma()` calls `defragment_dma_buffer()`
to move all the wanted data to the start of the DMA buffer and then
calls `comedi_buf_write_samples()` to copy it all to the comedi async
buffer. Those two functions used to be called from
`move_block_from_dma()` which was absorbed into
`interrupt_pci9118_ai_dma()`.
Reinstate `move_block_from_dma()` but rewrite it to copy data directly
from the wanted fragments of the DMA buffer to the comedi async buffer
without defragmenting the buffer first.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/staging/comedi/drivers/adl_pci9118.c | 67 +++++++++++++++++++---------
1 file changed, 46 insertions(+), 21 deletions(-)
diff --git a/drivers/staging/comedi/drivers/adl_pci9118.c b/drivers/staging/comedi/drivers/adl_pci9118.c
index c0ea733..2660358 100644
--- a/drivers/staging/comedi/drivers/adl_pci9118.c
+++ b/drivers/staging/comedi/drivers/adl_pci9118.c
@@ -502,29 +502,56 @@ static unsigned int valid_samples_in_act_dma_buf(struct comedi_device *dev,
return n_samples;
}
-static unsigned int defragment_dma_buffer(struct comedi_device *dev,
- struct comedi_subdevice *s,
- unsigned short *dma_buffer,
- unsigned int num_samples)
+static void move_block_from_dma(struct comedi_device *dev,
+ struct comedi_subdevice *s,
+ unsigned short *dma_buffer,
+ unsigned int n_raw_samples)
{
struct pci9118_private *devpriv = dev->private;
struct comedi_cmd *cmd = &s->async->cmd;
- unsigned int i = 0, j = 0;
- unsigned int start_pos = devpriv->ai_add_front,
- stop_pos = devpriv->ai_add_front + cmd->chanlist_len;
- unsigned int raw_scanlen = devpriv->ai_add_front + cmd->chanlist_len +
- devpriv->ai_add_back;
+ unsigned int start_pos = devpriv->ai_add_front;
+ unsigned int stop_pos = start_pos + cmd->chanlist_len;
+ unsigned int span_len = stop_pos + devpriv->ai_add_back;
+ unsigned int dma_pos = devpriv->ai_act_dmapos;
+ unsigned int x;
- for (i = 0; i < num_samples; i++) {
- if (devpriv->ai_act_dmapos >= start_pos &&
- devpriv->ai_act_dmapos < stop_pos) {
- dma_buffer[j++] = dma_buffer[i];
+ if (span_len == cmd->chanlist_len) {
+ /* All samples are to be copied. */
+ comedi_buf_write_samples(s, dma_buffer, n_raw_samples);
+ dma_pos += n_raw_samples;
+ } else {
+ /*
+ * Not all samples are to be copied. Buffer contents consist
+ * of a possibly non-whole number of spans and a region of
+ * each span is to be copied.
+ */
+ while (n_raw_samples) {
+ if (dma_pos < start_pos) {
+ /* Skip samples before start position. */
+ x = start_pos - dma_pos;
+ if (x > n_raw_samples)
+ x = n_raw_samples;
+ dma_pos += x;
+ n_raw_samples -= x;
+ if (!n_raw_samples)
+ break;
+ }
+ if (dma_pos < stop_pos) {
+ /* Copy samples before stop position. */
+ x = stop_pos - dma_pos;
+ if (x > n_raw_samples)
+ x = n_raw_samples;
+ comedi_buf_write_samples(s, dma_buffer, x);
+ dma_pos += x;
+ n_raw_samples -= x;
+ }
+ /* Advance to next span. */
+ start_pos += span_len;
+ stop_pos += span_len;
}
- devpriv->ai_act_dmapos++;
- devpriv->ai_act_dmapos %= raw_scanlen;
}
-
- return j;
+ /* Update position in span for next time. */
+ devpriv->ai_act_dmapos = dma_pos % span_len;
}
static void pci9118_exttrg_enable(struct comedi_device *dev, bool enable)
@@ -681,10 +708,8 @@ static void interrupt_pci9118_ai_dma(struct comedi_device *dev,
}
}
- if (n_all) {
- n_valid = defragment_dma_buffer(dev, s, dmabuf->virt, n_all);
- comedi_buf_write_samples(s, dmabuf->virt, n_valid);
- }
+ if (n_all)
+ move_block_from_dma(dev, s, dmabuf->virt, n_all);
if (!devpriv->ai_neverending) {
if (s->async->scans_done >= cmd->stop_arg)
--
2.1.3
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