staging: comedi: das16m1: don't calc pacer divisors twice

The analog input async command can use the pacer for the convert_src. The
(*do_cmdtest) calculates the divisors when validating the cmd argument.

There is no reason to recalc the divisors in the (*do_cmd). Just use the
values from the private data.

Refactor das16m1_set_pacer() to use the i8254_set_mode() and i8254_write()
helpers instead of i8254_load(). This allows us to use the I8254_* defines
when setting the mode to clarify the code.

Tidy up das16m1_cmd_exec() a bit. The pacer only needs to be set when the
convert_src is TRIG_TIMER.
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/das16m1.c

@@ -254,26 +254,16 @@ static int das16m1_cmd_test(struct comedi_device *dev,
 	return 0;
 }
 
-/* This function takes a time in nanoseconds and sets the     *
- * 2 pacer clocks to the closest frequency possible. It also  *
- * returns the actual sampling period.                        */
-static unsigned int das16m1_set_pacer(struct comedi_device *dev,
-				      unsigned int ns, int rounding_flags)
+static void das16m1_set_pacer(struct comedi_device *dev)
 {
 	struct das16m1_private_struct *devpriv = dev->private;
+	unsigned long timer_base = dev->iobase + DAS16M1_8254_SECOND;
 
-	i8253_cascade_ns_to_timer_2div(I8254_OSC_BASE_10MHZ,
-				       &devpriv->divisor1,
-				       &devpriv->divisor2,
-				       &ns, rounding_flags);
+	i8254_set_mode(timer_base, 0, 1, I8254_MODE2 | I8254_BINARY);
+	i8254_set_mode(timer_base, 0, 2, I8254_MODE2 | I8254_BINARY);
 
-	/* Write the values of ctr1 and ctr2 into counters 1 and 2 */
-	i8254_load(dev->iobase + DAS16M1_8254_SECOND, 0, 1, devpriv->divisor1,
-		   2);
-	i8254_load(dev->iobase + DAS16M1_8254_SECOND, 0, 2, devpriv->divisor2,
-		   2);
-
-	return ns;
+	i8254_write(timer_base, 0, 1, devpriv->divisor1);
+	i8254_write(timer_base, 0, 2, devpriv->divisor2);
 }
 
 static int das16m1_cmd_exec(struct comedi_device *dev,
@@ -307,10 +297,14 @@ static int das16m1_cmd_exec(struct comedi_device *dev,
 		outb(byte, dev->iobase + DAS16M1_QUEUE_DATA);
 	}
 
-	/* set counter mode and counts */
-	cmd->convert_arg =
-	    das16m1_set_pacer(dev, cmd->convert_arg,
-			      cmd->flags & TRIG_ROUND_MASK);
+	/* enable interrupts and set internal pacer counter mode and counts */
+	devpriv->control_state &= ~PACER_MASK;
+	if (cmd->convert_src == TRIG_TIMER) {
+		das16m1_set_pacer(dev);
+		devpriv->control_state |= INT_PACER;
+	} else {	/* TRIG_EXT */
+		devpriv->control_state |= EXT_PACER;
+	}
 
 	/*  set control & status register */
 	byte = 0;
@@ -323,13 +317,6 @@ static int das16m1_cmd_exec(struct comedi_device *dev,
 	/* clear interrupt bit */
 	outb(0, dev->iobase + DAS16M1_CLEAR_INTR);
 
-	/* enable interrupts and internal pacer */
-	devpriv->control_state &= ~PACER_MASK;
-	if (cmd->convert_src == TRIG_TIMER)
-		devpriv->control_state |= INT_PACER;
-	else
-		devpriv->control_state |= EXT_PACER;
-
 	devpriv->control_state |= INTE;
 	outb(devpriv->control_state, dev->iobase + DAS16M1_INTR_CONTROL);