linux-kernel - Re: [PATCH v3 2/4] dt-bindings: iio: magnetometer: ak8975: add gpio reset support

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Message-ID: <20200519132354.GB4623@gerhold.net>
Date:   Tue, 19 May 2020 15:23:54 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Jonathan Albrieux <jonathan.albrieux@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        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>,
        "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Steve Winslow <swinslow@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 2/4] dt-bindings: iio: magnetometer: ak8975: add gpio
 reset support

On Tue, May 19, 2020 at 02:43:52PM +0200, Jonathan Albrieux wrote:
> 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 datasheed says that, if not used, reset pin should be connected

datasheed -> datasheet

> to VID. This patch emulates this situation.
> 
> Signed-off-by: Jonathan Albrieux <jonathan.albrieux@...il.com>
> ---
>  .../devicetree/bindings/iio/magnetometer/ak8975.yaml          | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
> index 86e3efa693a8..a82c0ff5d098 100644
> --- a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
> +++ b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.yaml
> @@ -37,6 +37,9 @@ properties:
>    mount-matrix:
>      description: an optional 3x3 mounting rotation matrix
>  
> +  reset-gpio:
> +    description: an optional pin needed for AK09911 to set the reset state

Maybe add a comment that this should be "usually active low".

> +
>  required:
>    - compatible
>    - reg
> @@ -53,6 +56,7 @@ examples:
>              reg = <0x0c>;
>              gpios = <&gpj0 7 0>;
>              vdd-supply = <&ldo_3v3_gnss>;
> +            reset-gpio = <&msmgpio 111 1>;

Same here, reset-gpio = <&msmgpio 111 GPIO_ACTIVE_LOW>,
would be more clear.

>              mount-matrix = "-0.984807753012208",  /* x0 */
>                             "0",                   /* y0 */
>                             "-0.173648177666930",  /* z0 */
> -- 
> 2.17.1