staging: comedi: adl_pci9118: fix ai range/aref programming

Currently the analog input range and aref are set in setup_channel_list().
This works for the (*insn_read) but the (*do_cmd) has a problem.

In (*do_cmd) the ai control register is reset to 0 before the function works
out the bits needed to control the acquisition. This happens after the
setup_channel_list() call so the range is reset to bipolar and the aref to
single-ended.

Introduce a helper function, pci9118_ai_set_range_aref(), to handle the
programming of the range and aref bits. This function first clears the
cached value of the ai control register in the private data then sets the
appropriate bits. The (*insn_read) and (*do_cmd) can then set the other
bits needed to control the acquisition.

Then setup_channel_list() just needs to program the chanlist scan data.
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>

drivers/staging/comedi/drivers/adl_pci9118.c

@@ -318,6 +318,22 @@ static void pci9118_ai_reset_fifo(struct comedi_device *dev)
 	outl(0, dev->iobase + PCI9118_FIFO_RESET_REG);
 }
 
+static void pci9118_ai_set_range_aref(struct comedi_device *dev,
+				      struct comedi_subdevice *s,
+				      unsigned int chanspec)
+{
+	struct pci9118_private *devpriv = dev->private;
+	unsigned int range = CR_RANGE(chanspec);
+	unsigned int aref = CR_AREF(chanspec);
+
+	devpriv->AdControlReg = 0;
+	if (comedi_range_is_unipolar(s, range))
+		devpriv->AdControlReg |= PCI9118_AI_CTRL_UNIP;
+	if (aref == AREF_DIFF)
+		devpriv->AdControlReg |= PCI9118_AI_CTRL_DIFF;
+	outl(devpriv->AdControlReg, dev->iobase + PCI9118_AI_CTRL_REG);
+}
+
 static int check_channel_list(struct comedi_device *dev,
 			      struct comedi_subdevice *s, int n_chan,
 			      unsigned int *chanlist, int frontadd, int backadd)
@@ -371,33 +387,14 @@ static int setup_channel_list(struct comedi_device *dev,
 			      int backadd, int usedma)
 {
 	struct pci9118_private *devpriv = dev->private;
-	unsigned int i, differencial = 0, bipolar = 0;
 	unsigned int scanquad, gain, ssh = 0x00;
+	int i;
 
 	if (usedma == 1) {
 		rot = 8;
 		usedma = 0;
 	}
 
-	if (CR_AREF(chanlist[0]) == AREF_DIFF)
-		differencial = 1;	/* all input must be diff */
-	if (CR_RANGE(chanlist[0]) < PCI9118_BIPOLAR_RANGES)
-		bipolar = 1;	/* all input must be bipolar */
-
-	/* All is ok, so we can setup channel/range list */
-
-	if (!bipolar)
-		devpriv->AdControlReg |= PCI9118_AI_CTRL_UNIP;
-	else
-		devpriv->AdControlReg &= ~PCI9118_AI_CTRL_UNIP;
-
-	if (differencial)
-		devpriv->AdControlReg |= PCI9118_AI_CTRL_DIFF;
-	else
-		devpriv->AdControlReg &= ~PCI9118_AI_CTRL_DIFF;
-
-	outl(devpriv->AdControlReg, dev->iobase + PCI9118_AI_CTRL_REG);
-								/* setup mode */
 	/* gods know why this sequence! */
 	outl(2, dev->iobase + PCI9118_AI_AUTOSCAN_MODE_REG);
 	outl(0, dev->iobase + PCI9118_AI_AUTOSCAN_MODE_REG);
@@ -483,7 +480,12 @@ static int pci9118_insn_read_ai(struct comedi_device *dev,
 	int ret;
 	int n;
 
-	devpriv->AdControlReg = 0;
+       /*
+	* Configure analog input based on the chanspec.
+	* Acqusition is software controlled without interrupts.
+	*/
+	pci9118_ai_set_range_aref(dev, s, insn->chanspec);
+
 	devpriv->AdFunctionReg = PCI9118_AI_CFG_PDTRG | PCI9118_AI_CFG_PETRG;
 	outl(devpriv->AdFunctionReg, dev->iobase + PCI9118_AI_CFG_REG);
 						/*
@@ -1515,6 +1517,16 @@ static int pci9118_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 				cmd->chanlist, devpriv->ai_add_front,
 				devpriv->ai_add_back))
 		return -EINVAL;
+
+	/*
+	 * Configure analog input based on the first chanlist entry.
+	 * All entries are either unipolar or bipolar and single-ended
+	 * or differential.
+	 *
+	 * The acqusition control bits are enabled later.
+	 */
+	pci9118_ai_set_range_aref(dev, s, cmd->chanlist[0]);
+
 	if (!setup_channel_list(dev, s, cmd->chanlist_len,
 				cmd->chanlist, 0, devpriv->ai_add_front,
 				devpriv->ai_add_back, devpriv->usedma))
@@ -1570,12 +1582,6 @@ static int pci9118_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 
 	pci9118_start_pacer(dev, -1);	/* stop pacer */
 
-	devpriv->AdControlReg = 0;	/*
-					 * bipolar, S.E., use 8254, stop 8354,
-					 * internal trigger, soft trigger,
-					 * disable DMA
-					 */
-	outl(devpriv->AdControlReg, dev->iobase + PCI9118_AI_CTRL_REG);
 	devpriv->AdFunctionReg = PCI9118_AI_CFG_PDTRG | PCI9118_AI_CFG_PETRG;
 					/*
 					 * positive triggers, no S&H, no burst,