staging: comedi: ni_labpc_isadma: introduce labpc_isadma_disable()

Introduce a helper function to disable and the ISA DMA controller and
return the residue as described in Documentation/DMA-ISA-LPC.txt.

The DMA will always be disabled when labpc_setup_dma() is called. Remove
the unnecessary disable in that function.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/ni_labpc_isadma.c b/drivers/staging/comedi/drivers/ni_labpc_isadma.c
index 0ce8aad..862fb7e 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_labpc_isadma.c
+++ b/drivers/staging/comedi/drivers/ni_labpc_isadma.c
@@ -31,6 +31,19 @@
 /* size in bytes of dma buffer */
 #define LABPC_ISADMA_BUFFER_SIZE       0xff00
 
+static unsigned int labpc_isadma_disable(struct labpc_dma_desc *dma)
+{
+       unsigned long flags;
+       unsigned int residue;
+
+       flags = claim_dma_lock();
+       disable_dma(dma->chan);
+       residue = get_dma_residue(dma->chan);
+       release_dma_lock(flags);
+
+       return residue;
+}
+
 /* utility function that suggests a dma transfer size in bytes */
 static unsigned int labpc_suggest_transfer_size(struct comedi_device *dev,
                                                struct comedi_subdevice *s)
@@ -67,10 +80,10 @@ void labpc_setup_dma(struct comedi_device *dev, struct comedi_subdevice *s)
        unsigned long irq_flags;
 
        irq_flags = claim_dma_lock();
-       disable_dma(dma->chan);
        /* clear flip-flop to make sure 2-byte registers for
         * count and address get set correctly */
        clear_dma_ff(dma->chan);
+       set_dma_mode(dma->chan, DMA_MODE_READ);
        set_dma_addr(dma->chan, dma->hw_addr);
        /* set appropriate size of transfer */
        dma->size = labpc_suggest_transfer_size(dev, s);
@@ -99,20 +112,16 @@ void labpc_drain_dma(struct comedi_device *dev)
 
        status = devpriv->stat1;
 
-       flags = claim_dma_lock();
-       disable_dma(dma->chan);
-       /* clear flip-flop to make sure 2-byte registers for
-        * count and address get set correctly */
-       clear_dma_ff(dma->chan);
-
-       /* figure out how many points to read */
-       max_points = dma->size / sample_size;
-       /* residue is the number of points left to be done on the dma
+       /*
+        * residue is the number of bytes left to be done on the dma
         * transfer.  It should always be zero at this point unless
         * the stop_src is set to external triggering.
         */
-       residue = get_dma_residue(dma->chan) / sample_size;
-       num_points = max_points - residue;
+       residue = labpc_isadma_disable(dma);
+
+       /* figure out how many points to read */
+       max_points = dma->size / sample_size;
+       num_points = max_points - comedi_bytes_to_samples(s, residue);
        if (cmd->stop_src == TRIG_COUNT && devpriv->count < num_points)
                num_points = devpriv->count;
 
@@ -132,6 +141,8 @@ void labpc_drain_dma(struct comedi_device *dev)
                devpriv->count -= num_points;
 
        /* set address and count for next transfer */
+       flags = claim_dma_lock();
+       set_dma_mode(dma->chan, DMA_MODE_READ);
        set_dma_addr(dma->chan, dma->hw_addr);
        set_dma_count(dma->chan, leftover * sample_size);
        release_dma_lock(flags);
@@ -170,7 +181,6 @@ void labpc_init_dma_chan(struct comedi_device *dev, unsigned int dma_chan)
 {
        struct labpc_private *devpriv = dev->private;
        struct labpc_dma_desc *dma = &devpriv->dma_desc;
-       unsigned long dma_flags;
 
        if (dma_chan != 1 && dma_chan != 3)
                return;
@@ -187,10 +197,7 @@ void labpc_init_dma_chan(struct comedi_device *dev, unsigned int dma_chan)
 
        dma->chan = dma_chan;
 
-       dma_flags = claim_dma_lock();
-       disable_dma(dma->chan);
-       set_dma_mode(dma->chan, DMA_MODE_READ);
-       release_dma_lock(dma_flags);
+       labpc_isadma_disable(dma);
 }
 EXPORT_SYMBOL_GPL(labpc_init_dma_chan);