staging: comedi: ni_at_a2150: introduce a2150_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/ni_at_a2150.c b/drivers/staging/comedi/drivers/ni_at_a2150.c
index 23c59cb..73768d0 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_at_a2150.c
+++ b/drivers/staging/comedi/drivers/ni_at_a2150.c
@@ -172,12 +172,24 @@ static void a2150_isadma_program(struct a2150_dma_desc *dma)
        release_dma_lock(flags);
 }
 
+static unsigned int a2150_isadma_disable(struct a2150_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;
+}
+
 /* interrupt service routine */
 static irqreturn_t a2150_interrupt(int irq, void *d)
 {
        int i;
        int status;
-       unsigned long flags;
        struct comedi_device *dev = d;
        struct a2150_private *devpriv = dev->private;
        struct a2150_dma_desc *dma = &devpriv->dma_desc;
@@ -217,21 +229,16 @@ static irqreturn_t a2150_interrupt(int irq, void *d)
                return IRQ_HANDLED;
        }
 
-       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 = comedi_bytes_to_samples(s, dma->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 = comedi_bytes_to_samples(s, get_dma_residue(dma->chan));
-       release_dma_lock(flags);
-       num_points = max_points - residue;
+       residue = a2150_isadma_disable(dma);
+
+       /*  figure out how many points to read */
+       max_points = comedi_bytes_to_samples(s, dma->size);
+       num_points = max_points - comedi_bytes_to_samples(s, residue);
        if (devpriv->count < num_points && cmd->stop_src == TRIG_COUNT)
                num_points = devpriv->count;
 
@@ -288,7 +295,7 @@ static int a2150_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
        outw(devpriv->irq_dma_bits, dev->iobase + IRQ_DMA_CNTRL_REG);
 
        /*  disable computer's dma */
-       disable_dma(dma->chan);
+       a2150_isadma_disable(dma);
 
        /*  clear fifo and reset triggering circuitry */
        outw(0, dev->iobase + FIFO_RESET_REG);
@@ -524,7 +531,6 @@ static int a2150_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        unsigned long timer_base = dev->iobase + I8253_BASE_REG;
-       unsigned long lock_flags;
        unsigned int old_config_bits = devpriv->config_bits;
        unsigned int trigger_bits;
 
@@ -560,9 +566,7 @@ static int a2150_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
        /*  initialize number of samples remaining */
        devpriv->count = cmd->stop_arg * cmd->chanlist_len;
 
-       lock_flags = claim_dma_lock();
-       disable_dma(dma->chan);
-       release_dma_lock(lock_flags);
+       a2150_isadma_disable(dma);
 
        /*  set size of transfer to fill in 1/3 second */
 #define ONE_THIRD_SECOND 333333333
@@ -730,7 +734,7 @@ static void a2150_alloc_irq_dma(struct comedi_device *dev,
        dma->chan = dma_chan;
        devpriv->irq_dma_bits = IRQ_LVL_BITS(irq_num) | DMA_CHAN_BITS(dma_chan);
 
-       disable_dma(dma_chan);
+       a2150_isadma_disable(dma);
 }
 
 static void a2150_free_dma(struct comedi_device *dev)