[PATCH 3/5] iio: addac: ad74413r: implement support for optional refin-supply

[Rasmus Villemoes <linux@rasmusvillemoes.dk>]

The ad74412r/ad74413r has an internal 2.5V reference output, which (by
tying the REFOUT pin to the REFIN pin) can be used in lieu of an
external 2.5V input reference.

Support that case by using devm_regulator_get_optional(), and simply
hardcode the 2500000 uV in ad74413r_get_output_current_scale().

I'm not sure this is completely correct, but it's certainly better
than the current behaviour, where when refin-supply is not defined in
device tree, the regulator framework helpfully does its

  supply refin not found, using dummy regulator

thing. When we then do the regulator_get_voltage(), that dummy
regulator of course doesn't support that operation and thus returns
-22 (-EINVAL) which is used without being checked.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/iio/addac/ad74413r.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/addac/ad74413r.c b/drivers/iio/addac/ad74413r.c
index 37485be88a63..9f77d2f514de 100644
--- a/drivers/iio/addac/ad74413r.c
+++ b/drivers/iio/addac/ad74413r.c
@@ -608,7 +608,10 @@ static int ad74413r_get_output_voltage_scale(struct ad74413r_state *st,
 static int ad74413r_get_output_current_scale(struct ad74413r_state *st,
 					     int *val, int *val2)
 {
-	*val = regulator_get_voltage(st->refin_reg);
+	if (st->refin_reg)
+		*val = regulator_get_voltage(st->refin_reg);
+	else
+		*val = 2500000;
 	*val2 = st->sense_resistor_ohms * AD74413R_DAC_CODE_MAX * 1000;
 
 	return IIO_VAL_FRACTIONAL;
@@ -1313,19 +1316,25 @@ static int ad74413r_probe(struct spi_device *spi)
 	if (IS_ERR(st->regmap))
 		return PTR_ERR(st->regmap);
 
-	st->refin_reg = devm_regulator_get(st->dev, "refin");
-	if (IS_ERR(st->refin_reg))
-		return dev_err_probe(st->dev, PTR_ERR(st->refin_reg),
-				     "Failed to get refin regulator\n");
+	st->refin_reg = devm_regulator_get_optional(st->dev, "refin");
+	if (IS_ERR(st->refin_reg)) {
+		ret = PTR_ERR(st->refin_reg);
+		if (ret != -ENODEV)
+			return dev_err_probe(st->dev, ret,
+					     "Failed to get refin regulator\n");
+		st->refin_reg = NULL;
+	}
 
-	ret = regulator_enable(st->refin_reg);
-	if (ret)
-		return ret;
+	if (st->refin_reg) {
+		ret = regulator_enable(st->refin_reg);
+		if (ret)
+			return ret;
 
-	ret = devm_add_action_or_reset(st->dev, ad74413r_regulator_disable,
+		ret = devm_add_action_or_reset(st->dev, ad74413r_regulator_disable,
 				       st->refin_reg);
-	if (ret)
-		return ret;
+		if (ret)
+			return ret;
+	}
 
 	st->sense_resistor_ohms = 100000000;
 	device_property_read_u32(st->dev, "shunt-resistor-micro-ohms",
-- 
2.37.2