linux-kernel - [PATCH] iio: addac: ad74413: don't set DIN_SINK for functions other than digital input

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Date:   Wed,  3 May 2023 12:50:41 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iio: addac: ad74413: don't set DIN_SINK for functions other than digital input

Apparently, despite the name Digital Input Configuration Register, the
settings in the DIN_CONFIGx registers also affect other channel
functions. In particular, setting a non-zero value in the DIN_SINK
field breaks the resistance measurement function.

Now, one can of course argue that specifying a drive-strength-microamp
property along with a adi,ch-func which is not one of the digital
input functions is a bug in the device tree. However, we have a rather
complicated setup with instances of ad74412r on external hardware
modules, and have set a default drive-strength-microamp in our DT
fragments describing those, merely modifying the adi,ch-func settings
to reflect however the modules have been wired up. And restricting
this setting to just being done for digital input doesn't make the
driver any more complex.

Fixes: 504eb485589d1 (iio: ad74413r: wire up support for drive-strength-microamp property)
Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 drivers/iio/addac/ad74413r.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/addac/ad74413r.c b/drivers/iio/addac/ad74413r.c
index e3366cf5eb31..6b0e8218f150 100644
--- a/drivers/iio/addac/ad74413r.c
+++ b/drivers/iio/addac/ad74413r.c
@@ -1317,13 +1317,14 @@ static int ad74413r_setup_gpios(struct ad74413r_state *st)
 		}

 		if (config->func == CH_FUNC_DIGITAL_INPUT_LOGIC ||
-		    config->func == CH_FUNC_DIGITAL_INPUT_LOOP_POWER)
+		    config->func == CH_FUNC_DIGITAL_INPUT_LOOP_POWER) {
 			st->comp_gpio_offsets[comp_gpio_i++] = i;

-		strength = config->drive_strength;
-		ret = ad74413r_set_comp_drive_strength(st, i, strength);
-		if (ret)
-			return ret;
+			strength = config->drive_strength;
+			ret = ad74413r_set_comp_drive_strength(st, i, strength);
+			if (ret)
+				return ret;
+		}

 		ret = ad74413r_set_gpo_config(st, i, gpo_config);
 		if (ret)
-- 
2.37.2