From e87f65b238a6c1e76776469d92190f6c46c5817f Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Thu, 27 Nov 2014 11:37:19 +0000 Subject: staging: comedi: adl_pci9118: eliminate DMA buffer defragmentation step 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 Signed-off-by: Greg Kroah-Hartman --- 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 c0ea7335ed38..26603582e71a 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) -- cgit v1.2.3-55-g7522