[PATCH v5 6/6] iio: dac: ad5504: support scale via output-range-microvolt property

[Taha Ed-Dafili <0rayn.dev@gmail.com>]

The AD5504 output range is set by the R_SEL pin, not the VCC supply.
Add support for 'output-range-microvolt' to set vref_mv directly from
firmware. Use device_property_present() to distinguish absent from
malformed property rather than relying on the ambiguous -EINVAL from
device_property_read_u32_array(). Fall back to the vcc regulator
voltage for old DTs that predate this property.

Signed-off-by: Taha Ed-Dafili <0rayn.dev@gmail.com>
---
 drivers/iio/dac/ad5504.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/dac/ad5504.c b/drivers/iio/dac/ad5504.c
index 489d2e03e9f6..19ece5a2af58 100644
--- a/drivers/iio/dac/ad5504.c
+++ b/drivers/iio/dac/ad5504.c
@@ -300,6 +300,7 @@ static int ad5504_probe(struct spi_device *spi)
 	struct device *dev = &spi->dev;
 	struct iio_dev *indio_dev;
 	struct ad5504_state *st;
+	u32 range[2];
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
@@ -315,12 +316,30 @@ static int ad5504_probe(struct spi_device *spi)
 	if (is_acpi_device_node(dev_fwnode(dev))) {
 		st->vref_mv = AD5504_VREF_ACPI_DEFAULT_mV;
 	} else {
-		ret = devm_regulator_get_enable_read_voltage(dev, "vcc");
-		if (ret < 0)
-			return dev_err_probe(dev, ret,
-					     "Failed to get vcc regulator\n");
-
-		st->vref_mv = ret / 1000;
+		if (device_property_present(dev, "output-range-microvolt")) {
+			ret = device_property_read_u32_array(dev, "output-range-microvolt",
+							     range, ARRAY_SIZE(range));
+			if (ret)
+				return dev_err_probe(dev, ret,
+							"Error parsing output-range-microvolt\n");
+
+			if (range[0] != 0 || (range[1] != 30 * MICRO && range[1] != 60 * MICRO))
+				return dev_err_probe(dev, -EINVAL,
+					"Invalid output-range-microvolt\n");
+
+			st->vref_mv = range[1] / (MICRO / MILLI);
+
+			ret = devm_regulator_get_enable(dev, "vcc");
+			if (ret < 0)
+				return dev_err_probe(dev, ret, "Failed to enable vcc regulator\n");
+		} else {
+			/* Backward compat: old DTs without output-range-microvolt */
+			ret = devm_regulator_get_enable_read_voltage(dev, "vcc");
+			if (ret < 0)
+				return dev_err_probe(dev, ret, "Failed to get vcc regulator\n");
+
+			st->vref_mv = ret / (MICRO / MILLI);
+		}
 	}
 
 	st->spi = spi;
-- 
2.55.0