linux-kernel - Re: [PATCH v5 2/6] [media] ad5820: DT new optional field enable-gpios

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Date:   Tue, 2 Oct 2018 12:57:22 +0200
From:   Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Pavel Machek <pavel@....cz>, Sakari Ailus <sakari.ailus@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v5 2/6] [media] ad5820: DT new optional field enable-gpios

Hi Laurent
On Tue, Oct 2, 2018 at 12:35 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Tuesday, 2 October 2018 10:32:18 EEST Ricardo Ribalda Delgado wrote:
> > Document new enable-gpio field. It can be used to disable the part
> > without turning down its regulator.
> >
> > Cc: devicetree@...r.kernel.org
> > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> > Acked-by: Pavel Machek <pavel@....cz>
> > ---
> >  Documentation/devicetree/bindings/media/i2c/ad5820.txt | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> > b/Documentation/devicetree/bindings/media/i2c/ad5820.txt index
> > 5940ca11c021..9ccd96d3d5f0 100644
> > --- a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> > +++ b/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> > @@ -8,6 +8,12 @@ Required Properties:
> >
> >    - VANA-supply: supply of voltage for VANA pin
> >
> > +Optional properties:
> > +
> > +   - enable-gpios : GPIO spec for the XSHUTDOWN pin. Note that the polarity
> > of +the enable GPIO is the opposite of the XSHUTDOWN pin (asserting the
> > enable +GPIO deasserts the XSHUTDOWN signal and vice versa).
>
> After reading this one more time, I think the text is at the very least
> confusing. The logic level of the enable GPIO is the same as the logic level
> of the XSHUTDOWN pin. The latter being active low, asserting "enable" will
> deassert "shutdown", but talking about "desserting XSHUTDOWN" is confusing.
>

what about:

- enable-gpios : GPIO spec for the XSHUTDOWN pin. When the XSHUTDOWN pin
is asserted the device is enabled.

> > of +the enable GPIO is the opposite of the XSHUTDOWN pin (asserting the
> > enable +GPIO deasserts the XSHUTDOWN signal and vice versa).

> >  Example:
> >
> >         ad5820: coil@c {
> > @@ -15,5 +21,6 @@ Example:
> >                 reg = <0x0c>;
> >
> >                 VANA-supply = <&vaux4>;
> > +               enable-gpios = <&msmgpio 26 GPIO_ACTIVE_HIGH>;
> >         };
>
>
> --
> Regards,
>
> Laurent Pinchart
>
>
>


-- 
Ricardo Ribalda