diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
index 51846adf8340..2d684747a639 100644
--- a/drivers/staging/comedi/drivers/usbduxsigma.c
+++ b/drivers/staging/comedi/drivers/usbduxsigma.c
@@ -551,27 +551,6 @@ static int usbduxsigma_ai_cmdtest(struct comedi_device *dev,
 	if (err)
 		return 3;
 
-	/* Step 4: fix up any arguments */
-
-	if (high_speed) {
-		/*
-		 * every 2 channels get a time window of 125us. Thus, if we
-		 * sample all 16 channels we need 1ms. If we sample only one
-		 * channel we need only 125us
-		 */
-		devpriv->ai_interval = interval;
-		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
-	} else {
-		/* interval always 1ms */
-		devpriv->ai_interval = 1;
-		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
-	}
-	if (devpriv->ai_timer < 1)
-		err |= -EINVAL;
-
-	if (err)
-		return 4;
-
 	return 0;
 }
 
@@ -669,6 +648,22 @@ static int usbduxsigma_ai_cmd(struct comedi_device *dev,
 
 	down(&devpriv->sem);
 
+	if (devpriv->high_speed) {
+		/*
+		 * every 2 channels get a time window of 125us. Thus, if we
+		 * sample all 16 channels we need 1ms. If we sample only one
+		 * channel we need only 125us
+		 */
+		unsigned int interval = usbduxsigma_chans_to_interval(len);
+
+		devpriv->ai_interval = interval;
+		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
+	} else {
+		/* interval always 1ms */
+		devpriv->ai_interval = 1;
+		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
+	}
+
 	for (i = 0; i < len; i++) {
 		unsigned int chan  = CR_CHAN(cmd->chanlist[i]);