staging: comedi: pcmmio: return error if ao conversion times out

Rename wait_dac_ready() so it has namespace associated with the
driver.

Fix the function so it returns an errno if the conversion times
out. Propogate this errno if it happens.

Define the analog output status register to remove the magic numbers.
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>

drivers/staging/comedi/drivers/pcmmio.c

@@ -122,6 +122,14 @@ Configuration Options:
 #define PCMMIO_AO_CMD_CHAN_SEL(x)		(((x) & 0x03) << 1)
 #define PCMMIO_AO_CMD_CHAN_SEL_ALL		(0x0f << 0)
 #define PCMMIO_AO_STATUS_REG			0x0b
+#define PCMMIO_AO_STATUS_DATA_READY		(1 << 7)
+#define PCMMIO_AO_STATUS_DATA_DMA_PEND		(1 << 6)
+#define PCMMIO_AO_STATUS_CMD_DMA_PEND		(1 << 5)
+#define PCMMIO_AO_STATUS_IRQ_PEND		(1 << 4)
+#define PCMMIO_AO_STATUS_DATA_DRQ_ENA		(1 << 2)
+#define PCMMIO_AO_STATUS_REG_SEL		(1 << 3)
+#define PCMMIO_AO_STATUS_CMD_DRQ_ENA		(1 << 1)
+#define PCMMIO_AO_STATUS_IRQ_ENA		(1 << 0)
 #define PCMMIO_AO_RESOURCE_ENA_REG		0x0b
 #define PCMMIO_AO_2ND_DAC_OFFSET		0x04
 
@@ -885,22 +893,16 @@ static int ao_rinsn(struct comedi_device *dev, struct comedi_subdevice *s,
 	return n;
 }
 
-static int wait_dac_ready(unsigned long iobase)
+static int pcmmio_ao_wait_for_eoc(unsigned long iobase, unsigned int timeout)
 {
-	unsigned long retry = 100000L;
-
-	/* This may seem like an absurd way to handle waiting and violates the
-	   "no busy waiting" policy. The fact is that the hardware is
-	   normally so fast that we usually only need one time through the loop
-	   anyway. The longer timeout is for rare occasions and for detecting
-	   non-existent hardware.  */
+	unsigned char status;
 
-	while (retry--) {
-		if (inb(iobase + 3) & 0x80)
+	while (timeout--) {
+		status = inb(iobase + PCMMIO_AO_STATUS_REG);
+		if (status & PCMMIO_AO_STATUS_DATA_READY)
 			return 0;
-
 	}
-	return 1;
+	return -ETIME;
 }
 
 static int pcmmio_ao_insn_write(struct comedi_device *dev,
@@ -914,6 +916,7 @@ static int pcmmio_ao_insn_write(struct comedi_device *dev,
 	unsigned int range = CR_RANGE(insn->chanspec);
 	unsigned int val = devpriv->ao_readback[chan];
 	unsigned char cmd = 0;
+	int ret;
 	int i;
 
 	/*
@@ -932,7 +935,9 @@ static int pcmmio_ao_insn_write(struct comedi_device *dev,
 	outb(PCMMIO_AO_LSB_SPAN(range), iobase + PCMMIO_AO_LSB_REG);
 	outb(0, iobase + PCMMIO_AO_MSB_REG);
 	outb(cmd | PCMMIO_AO_CMD_WR_SPAN_UPDATE, iobase + PCMMIO_AO_CMD_REG);
-	wait_dac_ready(iobase);
+	ret = pcmmio_ao_wait_for_eoc(iobase, 100000);
+	if (ret)
+		return ret;
 
 	for (i = 0; i < insn->n; i++) {
 		val = data[i];
@@ -942,7 +947,9 @@ static int pcmmio_ao_insn_write(struct comedi_device *dev,
 		outb((val >> 8) & 0xff, iobase + PCMMIO_AO_MSB_REG);
 		outb(cmd | PCMMIO_AO_CMD_WR_CODE_UPDATE,
 		     iobase + PCMMIO_AO_CMD_REG);
-		wait_dac_ready(iobase);
+		ret = pcmmio_ao_wait_for_eoc(iobase, 100000);
+		if (ret)
+			return ret;
 
 		devpriv->ao_readback[chan] = val;
 	}