staging: comedi: das1800: introduce das1800_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.

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/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index 6df58cda7d3293b8ff03e6a1164df66391d1e256..6359fe665ed6df0cbc585db1e27fb2668d75c606 100644 (file)
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -465,6 +465,19 @@ static void das1800_isadma_program(struct das1800_dma_desc *dma)
        release_dma_lock(flags);
 }
 
+static unsigned int das1800_isadma_disable(unsigned int dma_chan)
+{
+       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;
+}
+
 static inline uint16_t munge_bipolar_sample(const struct comedi_device *dev,
                                            uint16_t sample)
 {
@@ -524,23 +537,16 @@ static void das1800_handle_fifo_not_empty(struct comedi_device *dev,
        }
 }
 
-/* Utility function used by das1800_flush_dma() and das1800_handle_dma().
- * Assumes dma lock is held */
+/* Utility function used by das1800_flush_dma() and das1800_handle_dma() */
 static void das1800_flush_dma_channel(struct comedi_device *dev,
                                      struct comedi_subdevice *s,
                                      struct das1800_dma_desc *dma)
 {
-       unsigned int nbytes;
+       unsigned int residue = das1800_isadma_disable(dma->chan);
+       unsigned int nbytes = dma->size - residue;
        unsigned int nsamples;
 
-       disable_dma(dma->chan);
-
-       /* clear flip-flop to make sure 2-byte registers
-        * get set correctly */
-       clear_dma_ff(dma->chan);
-
        /*  figure out how many points to read */
-       nbytes = dma->size - get_dma_residue(dma->chan);
        nsamples = comedi_bytes_to_samples(s, nbytes);
        nsamples = comedi_nsamples_left(s, nsamples);
 
@@ -555,10 +561,8 @@ static void das1800_flush_dma(struct comedi_device *dev,
 {
        struct das1800_private *devpriv = dev->private;
        struct das1800_dma_desc *dma = &devpriv->dma_desc[devpriv->cur_dma];
-       unsigned long flags;
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;
 
-       flags = claim_dma_lock();
        das1800_flush_dma_channel(dev, s, dma);
 
        if (dual_dma) {
@@ -568,8 +572,6 @@ static void das1800_flush_dma(struct comedi_device *dev,
                das1800_flush_dma_channel(dev, s, dma);
        }
 
-       release_dma_lock(flags);
-
        /*  get any remaining samples in fifo */
        das1800_handle_fifo_not_empty(dev, s);
 }
@@ -579,12 +581,9 @@ static void das1800_handle_dma(struct comedi_device *dev,
 {
        struct das1800_private *devpriv = dev->private;
        struct das1800_dma_desc *dma = &devpriv->dma_desc[devpriv->cur_dma];
-       unsigned long flags;
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;
 
-       flags = claim_dma_lock();
        das1800_flush_dma_channel(dev, s, dma);
-       release_dma_lock(flags);
 
        /* re-enable dma channel */
        das1800_isadma_program(dma);
@@ -611,7 +610,7 @@ static int das1800_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
        for (i = 0; i < 2; i++) {
                dma = &devpriv->dma_desc[i];
                if (dma->chan)
-                       disable_dma(dma->chan);
+                       das1800_isadma_disable(dma->chan);
        }
 
        return 0;
@@ -1233,7 +1232,6 @@ static int das1800_init_dma(struct comedi_device *dev,
        struct das1800_private *devpriv = dev->private;
        struct das1800_dma_desc *dma;
        unsigned int *dma_chan;
-       unsigned long flags;
        int i;
 
        /*
@@ -1292,9 +1290,7 @@ static int das1800_init_dma(struct comedi_device *dev,
                if (!dma->virt_addr)
                        return -ENOMEM;
 
-               flags = claim_dma_lock();
-               disable_dma(dma->chan);
-               release_dma_lock(flags);
+               das1800_isadma_disable(dma->chan);
        }
 
        return 0;