[PATCH v3 3/5] iio: adc: ad7192: Use VRef instead of AVdd as reference voltage source

[fl.scratchpad@gmail.com]

From: Fabrizio Lamarque <fl.scratchpad@gmail.com>

Add missing vref-supply and fix avdd-supply used as if it were vref.

AD7192 requires three independent voltage sources, digital supply (on
pin DVdd), analog supply (on AVdd) and reference voltage (VRef on
alternate pin pair REFIN1 or REFIN2).

Emit a warning message when AVdd is used in place of VRef for backwards
compatibility.

Fixes: b581f748cce0 ("staging: iio: adc: ad7192: move out of staging")
Signed-off-by: Fabrizio Lamarque <fl.scratchpad@gmail.com>
---
 drivers/iio/adc/ad7192.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
index 5a9c8898f8af..bc41323ea810 100644
--- a/drivers/iio/adc/ad7192.c
+++ b/drivers/iio/adc/ad7192.c
@@ -177,6 +177,7 @@ struct ad7192_chip_info {
 struct ad7192_state {
 	const struct ad7192_chip_info	*chip_info;
 	struct regulator		*avdd;
+	struct regulator		*vref;
 	struct clk			*mclk;
 	u16				int_vref_mv;
 	u32				fclk;
@@ -1014,11 +1015,31 @@ static int ad7192_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
+	st->vref = devm_regulator_get_optional(&spi->dev, "vref");
+	if (!IS_ERR(st->vref)) {
+		ret = regulator_enable(st->vref);
+		if (ret)
+			return dev_err_probe(&spi->dev, ret,
+					     "Failed to enable specified VRef supply\n");
+
+		ret = devm_add_action_or_reset(&spi->dev, ad7192_reg_disable, st->vref);
+		if (ret)
+			return ret;
+	} else if (PTR_ERR(st->vref) != -ENODEV) {
+		return PTR_ERR(st->vref);
+	}
+
 	ret = devm_regulator_get_enable(&spi->dev, "dvdd");
 	if (ret)
 		return dev_err_probe(&spi->dev, ret, "Failed to enable specified DVdd supply\n");
 
-	ret = regulator_get_voltage(st->avdd);
+
+	if (!IS_ERR(st->vref)) {
+		ret = regulator_get_voltage(st->vref);
+	} else {
+		dev_warn(&spi->dev, "Using AVdd in place of VRef. Likely an old DTS\n");
+		ret = regulator_get_voltage(st->avdd);
+	}
 	if (ret < 0) {
 		dev_err(&spi->dev, "Device tree error, reference voltage undefined\n");
 		return ret;
-- 
2.34.1