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

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Message-ID: <13152589.2v2DAIKa7y@avalon>
Date:   Tue, 02 Oct 2018 14:10:33 +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 <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 Ricardo,

On Tuesday, 2 October 2018 13:57:22 EEST Ricardo Ribalda Delgado wrote:
> On Tue, Oct 2, 2018 at 12:35 PM Laurent Pinchart wrote:
> > 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.

For some reason "asserting a pin" doesn't seem right to me. How about

- enable-gpios: GPIO spec for the XSHUTDOWN pin. The XSHUTDOWN signal is 
active low, a high level on the pin enables the device.

> > > 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


-- 
Regards,

Laurent Pinchart