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

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Message-ID: <20200519140930.GC30573@ict14-OptiPlex-980>
Date:   Tue, 19 May 2020 16:09:30 +0200
From:   Jonathan Albrieux <jonathan.albrieux@...il.com>
To:     Stephan Gerhold <stephan@...hold.net>
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 03:23:54PM +0200, Stephan Gerhold wrote:
> 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
>

Will fix that soon
 
> > 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

Thank you for the suggestions, will work on them,

Best regards,
Jonathan Albrieux