linux-kernel - [PATCH] iio: adc: ad7124: fix temperature channel

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Message-Id: <20250923-iio-adc-ad7124-fix-temperature-channel-v1-1-e421c98c0d72@baylibre.com>
Date: Tue, 23 Sep 2025 15:18:02 -0500
From: David Lechner <dlechner@...libre.com>
To: Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, 
 Uwe Kleine-König <u.kleine-koenig@...libre.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 David Lechner <dlechner@...libre.com>
Subject: [PATCH] iio: adc: ad7124: fix temperature channel

Fix temperature channel not working due to gain and offset not being
initialized. This was causing the raw temperature readings to be always
8388608 (0x800000).

To fix it, we just make sure the gain and offset values are set to the
default values and still return early without doing an internal
calibration.

While here, add a comment explaining why we don't bother calibrating
the temperature channel.

Fixes: 47036a03a303 ("iio: adc: ad7124: Implement internal calibration at probe time")
Signed-off-by: David Lechner <dlechner@...libre.com>
---
 drivers/iio/adc/ad7124.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 374e39736584f55c1290db3e257dff2c60f884d2..94d90a63987c0f9886586db0c4bc1690855be2c1 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -1518,10 +1518,6 @@ static int __ad7124_calibrate_all(struct ad7124_state *st, struct iio_dev *indio
 	int ret, i;
 
 	for (i = 0; i < st->num_channels; i++) {
-
-		if (indio_dev->channels[i].type != IIO_VOLTAGE)
-			continue;
-
 		/*
 		 * For calibration the OFFSET register should hold its reset default
 		 * value. For the GAIN register there is no such requirement but
@@ -1531,6 +1527,13 @@ static int __ad7124_calibrate_all(struct ad7124_state *st, struct iio_dev *indio
 		st->channels[i].cfg.calibration_offset = 0x800000;
 		st->channels[i].cfg.calibration_gain = st->gain_default;
 
+		/*
+		 * Only the main voltage input channels are important enough
+		 * to be automatically calibrated here.
+		 */
+		if (indio_dev->channels[i].type != IIO_VOLTAGE)
+			continue;
+
 		/*
 		 * Full-scale calibration isn't supported at gain 1, so skip in
 		 * that case. Note that untypically full-scale calibration has

---
base-commit: 411e8b72c181e4f49352c12ced0fd8426eb683aa
change-id: 20250923-iio-adc-ad7124-fix-temperature-channel-5900f7302886

Best regards,
-- 
David Lechner <dlechner@...libre.com>