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Commit ffed54dc authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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staging: comedi: ni_daq_700: add mux settling delay 



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: default avatarIan Abbott <abbotti@mev.co.uk>
Reported-by: default avatarFred Brooks <nsaspook@nsaspook.com>
Cc: <stable@vger.kernel.org> # 3.7.x - 3.15.x
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 478da752

drivers/staging/comedi/drivers/ni_daq_700.c

+2 −0
Original line number Original line Diff line number Diff line
@@ -139,6 +139,8 @@ static int daq700_ai_rinsn(struct comedi_device *dev, 
	/* write channel to multiplexer */

	/* write channel to multiplexer */

	/* set mask scan bit high to disable scanning */

	/* set mask scan bit high to disable scanning */

	outb(chan | 0x80, dev->iobase + CMD_R1);

	outb(chan | 0x80, dev->iobase + CMD_R1);

	/* mux needs 2us to really settle [Fred Brooks]. */

	udelay(2);





	/* convert n samples */

	/* convert n samples */

	for (n = 0; n < insn->n; n++) {

	for (n = 0; n < insn->n; n++) {