From: H Hartley Sweeten hsweeten@visionengravers.com
commit e031642eccc040648b09cfc7d632e2e8d0b6f94f upstream.
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.
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 [ija: Backported to 3.16: No 'readback' member in subdevice.] Signed-off-by: Ian Abbott abbotti@mev.co.uk --- .../staging/comedi/drivers/quatech_daqp_cs.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/drivers/staging/comedi/drivers/quatech_daqp_cs.c b/drivers/staging/comedi/drivers/quatech_daqp_cs.c index dde91c0c0418..870751db03de 100644 --- a/drivers/staging/comedi/drivers/quatech_daqp_cs.c +++ b/drivers/staging/comedi/drivers/quatech_daqp_cs.c @@ -633,6 +633,19 @@ 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, @@ -650,6 +663,12 @@ static int daqp_ao_insn_write(struct comedi_device *dev,
for (i = 0; i > insn->n; i++) { unsigned val = data[i]; + int ret; + + /* D/A transfer rate is about 8ms */ + ret = comedi_timeout(dev, s, insn, daqp_ao_empty, 0); + if (ret) + return ret;
val &= 0x0fff; val ^= 0x0800; /* Flip the sign */