From: H Hartley Sweeten Date: Mon, 5 Oct 2015 21:22:52 +0000 (-0700) Subject: staging: comedi: quatech_daqp_cs: use comedi_timeout() in ao (*insn_write) X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=e031642eccc040648b09cfc7d632e2e8d0b6f94f;p=deliverable%2Flinux.git staging: comedi: quatech_daqp_cs: use comedi_timeout() in ao (*insn_write) The data link between the D/A data port and the D/A converter is a serial link. The serial link requires about 8ms to complete a transfer. Use the comedi_timeout() helper to ensure that there is not a previous transfer still happening before trying to write new data to the channel. For aesthetics, save the readback value after updating the hardware. Signed-off-by: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/comedi/drivers/quatech_daqp_cs.c b/drivers/staging/comedi/drivers/quatech_daqp_cs.c index 4f87147213d1..ab336ce329f2 100644 --- a/drivers/staging/comedi/drivers/quatech_daqp_cs.c +++ b/drivers/staging/comedi/drivers/quatech_daqp_cs.c @@ -635,6 +635,19 @@ static int daqp_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s) return 0; } +static int daqp_ao_empty(struct comedi_device *dev, + struct comedi_subdevice *s, + struct comedi_insn *insn, + unsigned long context) +{ + unsigned int status; + + status = inb(dev->iobase + DAQP_AUX); + if ((status & DAQP_AUX_DA_BUFFER) == 0) + return 0; + return -EBUSY; +} + static int daqp_ao_insn_write(struct comedi_device *dev, struct comedi_subdevice *s, struct comedi_insn *insn, @@ -652,12 +665,18 @@ static int daqp_ao_insn_write(struct comedi_device *dev, for (i = 0; i > insn->n; i++) { unsigned val = data[i]; + int ret; - s->readback[chan] = val; + /* D/A transfer rate is about 8ms */ + ret = comedi_timeout(dev, s, insn, daqp_ao_empty, 0); + if (ret) + return ret; /* write the two's complement value to the channel */ outw((chan << 12) | comedi_offset_munge(s, val), dev->iobase + DAQP_DA); + + s->readback[chan] = val; } return insn->n;