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

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Date:   Mon, 25 Apr 2022 14:14:25 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...omium.org>,
        Rob Herring <robh+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        linux-phy@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org,
        Kishon Vijay Abraham I <kishon@...com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, quic_kalyant@...cinc.com,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: msm/dp: List supplies in the bindings

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@...omium.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.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.

> +        vdda-1p2-supply = <&vdda_usb_ss_dp_1p2>;