| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 48/78] staging: comedi: ni_daq_700: add mux settling delay | Date | Mon, 9 Jun 2014 15:48:28 -0700 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Ian Abbott <abbotti@mev.co.uk>
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>
--- drivers/staging/comedi/drivers/ni_daq_700.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/staging/comedi/drivers/ni_daq_700.c +++ b/drivers/staging/comedi/drivers/ni_daq_700.c @@ -122,6 +122,8 @@ static int daq700_ai_rinsn(struct comedi /* 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++) {
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