Re: [PATCH v4 6/9] dt-bindings: display: hdmi-connector: Add DDC power supply

[Rob Herring <robh@xxxxxxxxxx>]

On Fri, Apr 26, 2019 at 2:20 PM Ondřej Jirman <megous@xxxxxxxxxx> wrote:
>
> On Fri, Apr 26, 2019 at 01:23:37PM -0500, Rob Herring wrote:
> > On Sat, Apr 13, 2019 at 06:54:15PM +0200, megous@xxxxxxxxxx wrote:
> > > From: Ondrej Jirman <megous@xxxxxxxxxx>
> > >
> > > Some Allwinner SoC using boards (Orange Pi 3 for example) need to enable
> > > on-board voltage shifting logic for the DDC bus to be usable. Use
> > > ddc-supply on the hdmi-connector to model this.
> > >
> > > Add binding documentation for optional ddc-supply property.
> > >
> > > Signed-off-by: Ondrej Jirman <megous@xxxxxxxxxx>
> > > ---
> > >  .../devicetree/bindings/display/connector/hdmi-connector.txt     | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/connector/hdmi-connector.txt b/Documentation/devicetree/bindings/display/connector/hdmi-connector.txt
> > > index 508aee461e0d..33085aeb0bb9 100644
> > > --- a/Documentation/devicetree/bindings/display/connector/hdmi-connector.txt
> > > +++ b/Documentation/devicetree/bindings/display/connector/hdmi-connector.txt
> > > @@ -9,6 +9,7 @@ Optional properties:
> > >  - label: a symbolic name for the connector
> > >  - hpd-gpios: HPD GPIO number
> > >  - ddc-i2c-bus: phandle link to the I2C controller used for DDC EDID probing
> > > +- ddc-supply: the power supply for the DDC bus
> >
> > It's not just for DDC. It powers the chips in bridge dongles for
> > example. Pretty much every diagram I find just calls it 5V or +5V.
> >
> > So how about '5V-supply' or 'v5V-supply'?
>
> Just to be sure, the schematic that inspired this change looks like this:
>
> https://megous.com/dl/tmp/33b2971de6943e9d.png
>
> HDMI-5V is always on, and what is really being enabled here are mosfets
> connected to DDC_CEC_EN and not the HDMI-5V power supply. So in this case it
> really is just for DDC. It is conceivable that some boards may need both to
> enable 5V for HDMI circuitry and some separate power shifting logic for
> DDC bus.

Okay, not what I thought you were defining. DDC_CEC_EN is a GPIO line?
I wouldn't characterize this as a voltage rail, so I don't think it
should be a supply. Perhaps 'ddc-en-gpios'?

We certainly want to make it clear this is not the 5V supply.

Rob