iio: ad5064: Fix regulator handling

The correct way to handle errors returned by regualtor_get() and friends is
to propagate the error since that means that an regulator was specified,
but something went wrong when requesting it.

For handling optional regulators, e.g. when the device has an internal
vref, regulator_get_optional() should be used to avoid getting the dummy
regulator that the regulator core otherwise provides.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ad5064.c

@@ -808,6 +808,40 @@ static int ad5064_set_config(struct ad5064_state *st, unsigned int val)
 	return ad5064_write(st, cmd, 0, val, 0);
 }
 
+static int ad5064_request_vref(struct ad5064_state *st, struct device *dev)
+{
+	unsigned int i;
+	int ret;
+
+	for (i = 0; i < ad5064_num_vref(st); ++i)
+		st->vref_reg[i].supply = ad5064_vref_name(st, i);
+
+	if (!st->chip_info->internal_vref)
+		return devm_regulator_bulk_get(dev, ad5064_num_vref(st),
+					       st->vref_reg);
+
+	/*
+	 * This assumes that when the regulator has an internal VREF
+	 * there is only one external VREF connection, which is
+	 * currently the case for all supported devices.
+	 */
+	st->vref_reg[0].consumer = devm_regulator_get_optional(dev, "vref");
+	if (!IS_ERR(st->vref_reg[0].consumer))
+		return 0;
+
+	ret = PTR_ERR(st->vref_reg[0].consumer);
+	if (ret != -ENODEV)
+		return ret;
+
+	/* If no external regulator was supplied use the internal VREF */
+	st->use_internal_vref = true;
+	ret = ad5064_set_config(st, AD5064_CONFIG_INT_VREF_ENABLE);
+	if (ret)
+		dev_err(dev, "Failed to enable internal vref: %d\n", ret);
+
+	return ret;
+}
+
 static int ad5064_probe(struct device *dev, enum ad5064_type type,
 			const char *name, ad5064_write_func write)
 {
@@ -828,22 +862,11 @@ static int ad5064_probe(struct device *dev, enum ad5064_type type,
 	st->dev = dev;
 	st->write = write;
 
-	for (i = 0; i < ad5064_num_vref(st); ++i)
-		st->vref_reg[i].supply = ad5064_vref_name(st, i);
+	ret = ad5064_request_vref(st, dev);
+	if (ret)
+		return ret;
 
-	ret = devm_regulator_bulk_get(dev, ad5064_num_vref(st),
-		st->vref_reg);
-	if (ret) {
-		if (!st->chip_info->internal_vref)
-			return ret;
-		st->use_internal_vref = true;
-		ret = ad5064_set_config(st, AD5064_CONFIG_INT_VREF_ENABLE);
-		if (ret) {
-			dev_err(dev, "Failed to enable internal vref: %d\n",
-				ret);
-			return ret;
-		}
-	} else {
+	if (!st->use_internal_vref) {
 		ret = regulator_bulk_enable(ad5064_num_vref(st), st->vref_reg);
 		if (ret)
 			return ret;