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

[Sankeerth Billakanti <sbillaka@qti.qualcomm.com>]

Hi Doug,

>>
>> 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@chromium.org>
>> > ---
>> >
>> >  .../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.ya
>> > +++ ml
>> > @@ -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

Our internal power grid documents list the regulators as VDD_A_*_1P2 and VDD_A_*_0P9
for all the platforms.

So, as a practice, we put the same name in the DT files. Hence,

Reviewed-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>

Thank you,
Sankeerth