From ffed54dced86723f352323f15789d9ad6bee25e1 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 19 May 2014 11:29:04 +0100 Subject: [PATCH] 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: Ian Abbott Reported-by: Fred Brooks Cc: # 3.7.x - 3.15.x Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/ni_daq_700.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/staging/comedi/drivers/ni_daq_700.c b/drivers/staging/comedi/drivers/ni_daq_700.c index 171a71d..728bf7f 100644 --- a/drivers/staging/comedi/drivers/ni_daq_700.c +++ b/drivers/staging/comedi/drivers/ni_daq_700.c @@ -139,6 +139,8 @@ 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++) { -- 2.7.4