linux-kernel - [PATCH v4 2/4] dt-bindings: iio: magnetometer: ak8975: add gpio reset support

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Date:   Wed, 20 May 2020 09:31:14 +0200
From:   Jonathan Albrieux <jonathan.albrieux@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht,
        Jonathan Albrieux <jonathan.albrieux@...il.com>,
        Allison Randal <allison@...utok.net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
        DEVICE TREE BINDINGS),
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hartmut Knaack <knaack.h@....de>,
        Jilayne Lovejoy <opensource@...ayne.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio@...r.kernel.org (open list:IIO SUBSYSTEM AND DRIVERS),
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: [PATCH v4 2/4] dt-bindings: iio: magnetometer: ak8975: add gpio reset support

Add reset-gpio support.

Without reset's deassertion during ak8975_power_on(), driver's probe fails
on ak8975_who_i_am() while checking for device identity for AK09911 chip.

AK09911 has an active low reset gpio to handle register's reset.
AK09911 datasheet says that, if not used, reset pin should be connected
to VID. This patch emulates this situation.

Signed-off-by: Jonathan Albrieux <jonathan.albrieux@...il.com>
---
 .../devicetree/bindings/iio/magnetometer/ak8975.yaml        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
index 9d5b1e6908d1..d83f7e212658 100644
--- a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
+++ b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
@@ -41,6 +41,11 @@ properties:
   mount-matrix:
     description: an optional 3x3 mounting rotation matrix
 
+  reset-gpio:
+    description: |
+      an optional pin needed for AK09911 to set the reset state. This should
+      be usually active low
+
 required:
   - compatible
   - reg
@@ -58,6 +63,7 @@ examples:
             reg = <0x0c>;
             gpios = <&gpj0 7 GPIO_ACTIVE_HIGH>;
             vdd-supply = <&ldo_3v3_gnss>;
+            reset-gpio = <&msmgpio 111 GPIO_ACTIVE_LOW>;
             mount-matrix = "-0.984807753012208",  /* x0 */
                            "0",                   /* y0 */
                            "-0.173648177666930",  /* z0 */
-- 
2.17.1