linux-kernel - [PATCH 1/2] iio: adc: ad799x: add reference voltage capability to chip

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Message-ID: <20250806090158.117628-2-stefano.manni@gmail.com>
Date: Wed,  6 Aug 2025 11:01:57 +0200
From: Stefano Manni <stefano.manni@...il.com>
To: lars@...afoo.de,
	Michael.Hennerich@...log.com,
	jic23@...nel.org,
	dlechner@...libre.com,
	nuno.sa@...log.com,
	andy@...nel.org
Cc: linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Stefano Manni <stefano.manni@...il.com>
Subject: [PATCH 1/2] iio: adc: ad799x: add reference voltage capability to chip_info

If the chip supports an external reference voltage
on REFIN pin then the "vref-supply" regulator may be used.

This commit partially refactors 6b104e7895ab16b9b7f466c5f2ca282b87f661e8
to add the capability of the chip to have an external
voltage reference and then remove the ugly conditional check
on chip id.

Signed-off-by: Stefano Manni <stefano.manni@...il.com>
---
 drivers/iio/adc/ad799x.c | 45 +++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 9c02f9199139..955d845407b9 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -114,11 +114,13 @@ struct ad799x_chip_config {
  * @num_channels:	number of channels
  * @noirq_config:	device configuration w/o IRQ
  * @irq_config:		device configuration w/IRQ
+ * @has_vref:		device supports external reference voltage
  */
 struct ad799x_chip_info {
 	int				num_channels;
 	const struct ad799x_chip_config	noirq_config;
 	const struct ad799x_chip_config	irq_config;
+	bool has_vref;
 };
 
 struct ad799x_state {
@@ -604,6 +606,7 @@ static const struct iio_event_spec ad799x_events[] = {
 static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	[ad7991] = {
 		.num_channels = 5,
+		.has_vref = true,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 12),
@@ -617,6 +620,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7995] = {
 		.num_channels = 5,
+		.has_vref = true,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 10),
@@ -630,6 +634,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7999] = {
 		.num_channels = 5,
+		.has_vref = true,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 8),
@@ -643,6 +648,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7992] = {
 		.num_channels = 3,
+		.has_vref = false,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 12),
@@ -663,6 +669,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7993] = {
 		.num_channels = 5,
+		.has_vref = false,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 10),
@@ -687,6 +694,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7994] = {
 		.num_channels = 5,
+		.has_vref = false,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 12),
@@ -711,6 +719,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7997] = {
 		.num_channels = 9,
+		.has_vref = false,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 10),
@@ -743,6 +752,7 @@ static const struct ad799x_chip_info ad799x_chip_info_tbl[] = {
 	},
 	[ad7998] = {
 		.num_channels = 9,
+		.has_vref = false,
 		.noirq_config = {
 			.channel = {
 				AD799X_CHANNEL(0, 12),
@@ -809,34 +819,31 @@ static int ad799x_probe(struct i2c_client *client)
 		return ret;
 
 	/* check if an external reference is supplied */
-	st->vref = devm_regulator_get_optional(&client->dev, "vref");
-
-	if (IS_ERR(st->vref)) {
-		if (PTR_ERR(st->vref) == -ENODEV) {
-			st->vref = NULL;
-			dev_info(&client->dev, "Using VCC reference voltage\n");
-		} else {
-			ret = PTR_ERR(st->vref);
-			goto error_disable_reg;
+	if (chip_info->has_vref) {
+		st->vref = devm_regulator_get_optional(&client->dev, "vref");
+
+		if (IS_ERR(st->vref)) {
+			if (PTR_ERR(st->vref) == -ENODEV) {
+				st->vref = NULL;
+				dev_info(&client->dev, "Using VCC reference voltage\n");
+			} else {
+				ret = PTR_ERR(st->vref);
+				goto error_disable_reg;
+			}
 		}
-	}
 
-	if (st->vref) {
-		/*
-		 * Use external reference voltage if supported by hardware.
-		 * This is optional if voltage / regulator present, use VCC otherwise.
-		 */
-		if ((st->id == ad7991) || (st->id == ad7995) || (st->id == ad7999)) {
+		if (st->vref) {
 			dev_info(&client->dev, "Using external reference voltage\n");
 			extra_config |= AD7991_REF_SEL;
 			ret = regulator_enable(st->vref);
 			if (ret)
 				goto error_disable_reg;
-		} else {
-			st->vref = NULL;
-			dev_warn(&client->dev, "Supplied reference not supported\n");
 		}
 	}
+	else {
+		st->vref = NULL;
+		dev_dbg(&client->dev, "Supplied reference not supported\n");
+	}
 
 	st->client = client;
 
-- 
2.48.1