queue/staging-comedi-ni_labpc-set-up-command4-register-aft.patch

From 067c94ea8da1d140e9b567d07cf24e8eab634fe8 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 1 Feb 2013 14:51:57 +0000
Subject: [PATCH] staging: comedi: ni_labpc: set up command4 register *after*
 command3

commit 22056e2b46246d97ff0f7c6e21a77b8daa07f02c upstream.

Tuomas <tvainikk _at_ gmail _dot_ com> reported problems getting
meaningful output from a Lab-PC+ in differential mode for AI cmds, but
AI insn reads gave correct readings.  He tracked it down to two
problems, one of which is addressed by this patch.

It seems that writing to the command3 register after writing to the
command4 register in `labpc_ai_cmd()` messes up the differential
reference bit setting in the command4 register.  Set up the command4
register after the command3 register (as in `labpc_ai_rinsn()`) to avoid
the problem.

Thanks to Tuomas for suggesting the fix.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/staging/comedi/drivers/ni_labpc.c b/drivers/staging/comedi/drivers/ni_labpc.c
index 9521b04..7a310e9 100644
--- a/drivers/staging/comedi/drivers/ni_labpc.c
+++ b/drivers/staging/comedi/drivers/ni_labpc.c
@@ -1241,21 +1241,6 @@ static int labpc_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 		devpriv->write_byte(devpriv->command1_bits,
 				    dev->iobase + COMMAND1_REG);
 	}
-	/*  setup any external triggering/pacing (command4 register) */
-	devpriv->command4_bits = 0;
-	if (cmd->convert_src != TRIG_EXT)
-		devpriv->command4_bits |= EXT_CONVERT_DISABLE_BIT;
-	/* XXX should discard first scan when using interval scanning
-	 * since manual says it is not synced with scan clock */
-	if (labpc_use_continuous_mode(cmd) == 0) {
-		devpriv->command4_bits |= INTERVAL_SCAN_EN_BIT;
-		if (cmd->scan_begin_src == TRIG_EXT)
-			devpriv->command4_bits |= EXT_SCAN_EN_BIT;
-	}
-	/*  single-ended/differential */
-	if (aref == AREF_DIFF)
-		devpriv->command4_bits |= ADC_DIFF_BIT;
-	devpriv->write_byte(devpriv->command4_bits, dev->iobase + COMMAND4_REG);
 
 	devpriv->write_byte(cmd->chanlist_len,
 			    dev->iobase + INTERVAL_COUNT_REG);
@@ -1333,6 +1318,22 @@ static int labpc_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 		devpriv->command3_bits &= ~ADC_FNE_INTR_EN_BIT;
 	devpriv->write_byte(devpriv->command3_bits, dev->iobase + COMMAND3_REG);
 
+	/*  setup any external triggering/pacing (command4 register) */
+	devpriv->command4_bits = 0;
+	if (cmd->convert_src != TRIG_EXT)
+		devpriv->command4_bits |= EXT_CONVERT_DISABLE_BIT;
+	/* XXX should discard first scan when using interval scanning
+	 * since manual says it is not synced with scan clock */
+	if (labpc_use_continuous_mode(cmd) == 0) {
+		devpriv->command4_bits |= INTERVAL_SCAN_EN_BIT;
+		if (cmd->scan_begin_src == TRIG_EXT)
+			devpriv->command4_bits |= EXT_SCAN_EN_BIT;
+	}
+	/*  single-ended/differential */
+	if (aref == AREF_DIFF)
+		devpriv->command4_bits |= ADC_DIFF_BIT;
+	devpriv->write_byte(devpriv->command4_bits, dev->iobase + COMMAND4_REG);
+
 	/*  startup aquisition */
 
 	/*  command2 reg */
-- 
1.8.1.2