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

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Message-ID: <2128166.ZAkUExjJHM@avalon>
Date:   Tue, 02 Oct 2018 13:35:40 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     Pavel Machek <pavel@....cz>, Sakari Ailus <sakari.ailus@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, 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 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.

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


-- 
Regards,

Laurent Pinchart