From: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Ian Abbott <abbotti@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[ija: Backported to 3.16: No 'readback' member in subdevice.]
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
.../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 */
--
2.19.1
