From: Ian Abbott <abbotti@mev.co.uk>
Date: Mon, 19 May 2014 10:29:04 +0000 (+0100)
Subject: staging: comedi: ni_daq_700: add mux settling delay
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=f3c0ca9b1ac4282922f6ef75fef5f7cb9f913cfc;p=linux-edison.git

staging: comedi: ni_daq_700: add mux settling delay

commit ffed54dced86723f352323f15789d9ad6bee25e1 upstream.

I got a patch from the original author, Fred Brooks, to add a small
settling delay after setting the AI channel multiplexor.  The lack of
delay resulted in unstable or scrambled data on faster processors.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reported-by: Fred Brooks <nsaspook@nsaspook.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/staging/comedi/drivers/ni_daq_700.c b/drivers/staging/comedi/drivers/ni_daq_700.c
index d067ef70e19..5e80d428e54 100644
--- a/drivers/staging/comedi/drivers/ni_daq_700.c
+++ b/drivers/staging/comedi/drivers/ni_daq_700.c
@@ -127,6 +127,8 @@ static int daq700_ai_rinsn(struct comedi_device *dev,
 	/* write channel to multiplexer */
 	/* set mask scan bit high to disable scanning */
 	outb(chan | 0x80, dev->iobase + CMD_R1);
+	/* mux needs 2us to really settle [Fred Brooks]. */
+	udelay(2);
 
 	/* convert n samples */
 	for (n = 0; n < insn->n; n++) {