release/5.2.37/iio-adc-ad7124-Fix-DT-channel-configuration.patch

From 1b2003df384e452e8277a2f88141f1a8235d17a2 Mon Sep 17 00:00:00 2001
From: Alexandru Tachici <alexandru.tachici@analog.com>
Date: Fri, 20 Dec 2019 12:07:19 +0200
Subject: [PATCH] iio: adc: ad7124: Fix DT channel configuration

commit d7857e4ee1ba69732b16c73b2f2dde83ecd78ee4 upstream.

This patch fixes device tree channel configuration.

ad7124 driver reads channels configuration from the device tree.
It expects to find channel specifications as child nodes.
Before this patch ad7124 driver assumed that the child nodes are parsed
by for_each_available_child_of_node in the order 0,1,2,3...

This is wrong and the real order of the children can be seen by running:
dtc -I fs /sys/firmware/devicetree/base on the machine.

For example, running this on an rpi 3B+ yields the real
children order: 4,2,0,7,5,3,1,6

Before this patch the driver assigned the channel configuration
like this:
        - 0 <- 4
        - 1 <- 2
        - 2 <- 0
        ........
For example, the symptoms can be observed by connecting the 4th channel
to a 1V tension and then reading the in_voltage0-voltage19_raw sysfs
(multiplied of course by the scale) one would see that channel 0
measures 1V and channel 4 measures only noise.

Now the driver uses the reg property of each child in order to
correctly identify to which channel the parsed configuration
belongs to.

Fixes b3af341bbd966: ("iio: adc: Add ad7124 support")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 5262d34ebea8..2d662dd09e6b 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -485,13 +485,11 @@ static int ad7124_of_parse_channel_config(struct iio_dev *indio_dev,
 		else
 			st->channel_config[channel].refsel = tmp;
 
-		*chan = ad7124_channel_template;
-		chan->address = channel;
-		chan->scan_index = channel;
-		chan->channel = ain[0];
-		chan->channel2 = ain[1];
-
-		chan++;
+		chan[channel] = ad7124_channel_template;
+		chan[channel].address = channel;
+		chan[channel].scan_index = channel;
+		chan[channel].channel = ain[0];
+		chan[channel].channel2 = ain[1];
 	}
 
 	return 0;
-- 
2.7.4