patch "iio: adc: ad7124: Disable all channels at probe time" added to char-misc-linus

patch "iio: adc: ad7124: Disable all channels at probe time" added to char-misc-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio: adc: ad7124: Disable all channels at probe time

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From 4be339af334c283a1a1af3cb28e7e448a0aa8a7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@baylibre.com>
Date: Mon, 4 Nov 2024 11:19:04 +0100
Subject: iio: adc: ad7124: Disable all channels at probe time
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When during a measurement two channels are enabled, two measurements are
done that are reported sequencially in the DATA register. As the code
triggered by reading one of the sysfs properties expects that only one
channel is enabled it only reads the first data set which might or might
not belong to the intended channel.

To prevent this situation disable all channels during probe. This fixes
a problem in practise because the reset default for channel 0 is
enabled. So all measurements before the first measurement on channel 0
(which disables channel 0 at the end) might report wrong values.

Fixes: 7b8d045e497a ("iio: adc: ad7124: allow more than 8 channels")
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/20241104101905.845737-2-u.kleine-koenig@baylibre.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/adc/ad7124.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 7314fb32bdec..3d678c420cbf 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -917,6 +917,9 @@ static int ad7124_setup(struct ad7124_state *st)
 		 * set all channels to this default value.
 		 */
 		ad7124_set_channel_odr(st, i, 10);
+
+		/* Disable all channels to prevent unintended conversions. */
+		ad_sd_write_reg(&st->sd, AD7124_CHANNEL(i), 2, 0);
 	}
 
 	ret = ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
-- 
2.47.1