staging: comedi: pcl816: simplify the dma->size calculations

[firefly-linux-kernel-4.4.55.git] / drivers / staging / comedi / drivers / pcl816.c

diff --git a/drivers/staging/comedi/drivers/pcl816.c b/drivers/staging/comedi/drivers/pcl816.c
index 09fa40904daad09dbe2f0021a08e8a536b2844c8..88c89df717e5e75746333d2d600d3dfea2c66e90 100644 (file)
--- a/drivers/staging/comedi/drivers/pcl816.c
+++ b/drivers/staging/comedi/drivers/pcl816.c
@@ -115,8 +115,6 @@ static const struct pcl816_board boardtypes[] = {
 
 struct pcl816_private {
        struct comedi_isadma *dma;
-       long dma_runs_to_end;   /*  how many we must permorm DMA transfer to end of record */
-       unsigned long last_dma_run;     /*  how many bytes we must transfer on last DMA page */
        unsigned int ai_poll_ptr;       /*  how many sampes transfer poll */
        unsigned int divisor1;
        unsigned int divisor2;
@@ -149,53 +147,47 @@ static void pcl816_ai_setup_dma(struct comedi_device *dev,
        struct pcl816_private *devpriv = dev->private;
        struct comedi_isadma *dma = devpriv->dma;
        struct comedi_isadma_desc *desc = &dma->desc[0];
-       struct comedi_cmd *cmd = &s->async->cmd;
-
-       if (cmd->stop_src == TRIG_COUNT) {
-               /*  how many */
-               desc->size = cmd->stop_arg * comedi_bytes_per_scan(s);
-
-               /*  how many DMA pages we must fill */
-               devpriv->dma_runs_to_end = desc->size / desc->maxsize;
-
-               /* on last dma transfer must be moved */
-               devpriv->last_dma_run = desc->size % desc->maxsize;
-               devpriv->dma_runs_to_end--;
-               if (devpriv->dma_runs_to_end >= 0)
-                       desc->size = desc->maxsize;
-       } else {
-               desc->size = desc->maxsize;
-               devpriv->dma_runs_to_end = -1;
-       }
+       unsigned int nsamples;
 
        dma->cur_dma = 0;
 
+       /*
+        * Determine dma size based on the buffer maxsize and the number of
+        * samples remaining in the command.
+        */
+       nsamples = comedi_bytes_to_samples(s, desc->maxsize);
+       nsamples = comedi_nsamples_left(s, nsamples);
+       desc->size = comedi_samples_to_bytes(s, nsamples);
        comedi_isadma_program(desc);
 }
 
 static void pcl816_ai_setup_next_dma(struct comedi_device *dev,
-                                    struct comedi_subdevice *s)
+                                    struct comedi_subdevice *s,
+                                    unsigned int unread_samples)
 {
        struct pcl816_private *devpriv = dev->private;
-       struct comedi_cmd *cmd = &s->async->cmd;
        struct comedi_isadma *dma = devpriv->dma;
+       struct comedi_isadma_desc *desc;
+       unsigned int max_samples;
+       unsigned int nsamples;
 
        comedi_isadma_disable(dma->chan);
-       dma->cur_dma = 1 - dma->cur_dma;
-
-       /* switch dma bufs if still running */
-       if (devpriv->dma_runs_to_end > -1 || cmd->stop_src == TRIG_NONE) {
-               struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
-
-               if (devpriv->dma_runs_to_end)
-                       desc->size = desc->maxsize;
-               else
-                       desc->size = devpriv->last_dma_run;
 
+       dma->cur_dma = 1 - dma->cur_dma;
+       desc = &dma->desc[dma->cur_dma];
+
+       /*
+        * Determine dma size based on the buffer maxsize plus the number of
+        * unread samples and the number of samples remaining in the command.
+        */
+       max_samples = comedi_bytes_to_samples(s, desc->maxsize);
+       nsamples = max_samples + unread_samples;
+       nsamples = comedi_nsamples_left(s, nsamples);
+       if (nsamples > unread_samples) {
+               nsamples -= unread_samples;
+               desc->size = comedi_samples_to_bytes(s, nsamples);
                comedi_isadma_program(desc);
        }
-
-       devpriv->dma_runs_to_end--;
 }
 
 static void pcl816_ai_set_chan_range(struct comedi_device *dev,
@@ -324,13 +316,13 @@ static irqreturn_t pcl816_interrupt(int irq, void *d)
                return IRQ_HANDLED;
        }
 
-       pcl816_ai_setup_next_dma(dev, s);
-
        nsamples = comedi_bytes_to_samples(s, desc->size) -
                   devpriv->ai_poll_ptr;
        bufptr = devpriv->ai_poll_ptr;
        devpriv->ai_poll_ptr = 0;
 
+       pcl816_ai_setup_next_dma(dev, s, nsamples);
+
        transfer_from_dma_buf(dev, s, desc->virt_addr, bufptr, nsamples);
 
        pcl816_ai_clear_eoc(dev);