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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 <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten 2015-10-05 14:22:52 -07:00 committed by Greg Kroah-Hartman
parent 1271dd24c6
commit e031642ecc
1 changed files with 20 additions and 1 deletions
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21
drivers/staging/comedi/drivers/quatech_daqp_cs.c
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@ -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;