Re: [PATCH 1/2] dt-bindings: msm/dp: List supplies in the bindings

[Doug Anderson]

Hi,

On Mon, Apr 25, 2022 at 2:14 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote:
>
> Quoting Douglas Anderson (2022-04-25 14:06:42)
> > We're supposed to list the supplies in the dt bindings but there are
> > none in the DP controller bindings. Looking at the Linux driver and
> > existing device trees, we can see that two supplies are expected:
> > - vdda-0p9-supply
> > - vdda-1p2-supply
> >
> > Let's list them both in the bindings. Note that the datasheet for
> > sc7280 doesn't describe these supplies very verbosely. For the 0p9
> > supply, for instance, it says "Power for eDP 0.9 V circuits". This
> > this is obvious from the property name, we don't bother cluttering the
> > bindings with a description.
> >
> > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > ---
> >
> >  .../devicetree/bindings/display/msm/dp-controller.yaml      | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > index cd05cfd76536..dba31108db51 100644
> > --- a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > +++ b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > @@ -76,6 +76,9 @@ properties:
> >    "#sound-dai-cells":
> >      const: 0
> >
> > +  vdda-0p9-supply: true
> > +  vdda-1p2-supply: true
> > +
> >    ports:
> >      $ref: /schemas/graph.yaml#/properties/ports
> >      properties:
> > @@ -137,6 +140,9 @@ examples:
> >
> >          power-domains = <&rpmhpd SC7180_CX>;
> >
> > +        vdda-0p9-supply = <&vdda_usb_ss_dp_core>;
>
> Having 'a' in 'vdda' typically means 'analog' for 'analog' circuits, so
> I'd expect this to only matter for the phy that contains the analog
> circuitry. It would be great to remove the regulator code from
> drivers/gpu/drm/msm/dp/dp_power.c and move the regulator_set_load() call
> to the phy driver if possible. Hopefully qcom folks can help clarify
> here.

Interesting. Oddly enough, the sc7280 datasheet doesn't list the "_A".
It calls these "VDD_VREF_0P9" and "VDD_VREF_1P2". However, on the
schematic in front of me someone labeled these pins on the sc7280 with
the "A". ...and the driver looks for a supply with the "a". :-/

It would be good to get clarification from someone with better information.

-Doug