Re: [PATCH 3/4] [media] ad5820: DT new optional field enable-gpios

Laurent Pinchart
2018-09-21T02:08:44Z

On Thursday, 20 September 2018 23:21:28 EEST Laurent Pinchart wrote:
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Thursday, 20 September 2018 19:19:11 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@vger.kernel.org
> > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > ---
> >
> > Documentation/devicetree/bindings/media/i2c/ad5820.txt | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> > b/Documentation/devicetree/bindings/media/i2c/ad5820.txt index
> > 5940ca11c021..07d577bb37f7 100644
> > --- a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> > +++ b/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> >
> > @@ -8,6 +8,11 @@ Required Properties:
> > - VANA-supply: supply of voltage for VANA pin
> >
> > +Optional properties:
> > +
> > + - enable-gpios : GPIO spec for the XSHUTDOWN pin.
>
> xshutdown is active-low, so enable is active-high. Should this be documented
> explicitly, to avoid polarity errors ? Maybe something along the lines of
>
> - 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).

Or alternatively you could name the property xshutdown-gpios, as explained in
my (incorrect) review of 2/4.

> > If specified, it will be
> > + asserted when VANA-supply is enabled.
>
> That documents a driver behaviour, is it needed in DT ?
>
> > Example:
> > ad5820: coil@c {
> >
> > @@ -15,5 +20,6 @@ Example:
> > reg = <0x0c>;
> > VANA-supply = <&vaux4>;
> >
> > + enable-gpios = <&msmgpio 26 GPIO_ACTIVE_HIGH>;
> > };

--
Regards,

Laurent Pinchart