linux-kernel - Re: [PATCH v3 2/3] dt-bindings: phy: qcom-edp: Add X1E80100 PHY compatibles

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Date:   Fri, 8 Dec 2023 14:17:31 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Abel Vesa <abel.vesa@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Johan Hovold <johan@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] dt-bindings: phy: qcom-edp: Add X1E80100 PHY compatibles

On Fri, 8 Dec 2023 at 13:45, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 08/12/2023 12:04, Dmitry Baryshkov wrote:
> > On Fri, 8 Dec 2023 at 09:47, Krzysztof Kozlowski
> > <krzysztof.kozlowski@...aro.org> wrote:
> >>
> >> On 07/12/2023 20:16, Konrad Dybcio wrote:
> >>>
> >>>
> >>> On 12/7/23 17:51, Krzysztof Kozlowski wrote:
> >>>
> >>> [...]
> >>>
> >>>>> +allOf:
> >>>>> +  - if:
> >>>>> +      properties:
> >>>>> +        compatible:
> >>>>> +          contains:
> >>>>> +            enum:
> >>>>> +              - qcom,x1e80100-dp-phy
> >>>>> +    then:
> >>>>> +      properties:
> >>>>> +        phy-type:
> >>>>> +          description: DP (default) or eDP type
> >>>>
> >>>> Properties must be defined in top-level "properties:" block. In
> >>>> allOf:if:then you only disallow them for other variants.
> >>>>
> >>>>> +          enum: [ 6, 13 ]
> >>>>> +          default: 6
> >>>>
> >>>> Anyway, I was thinking this should be rather argument to phy-cells.
> >>> I'm not sure I'm for this, because the results would be:
> >>>
> >>> --- device.dts ---
> >>> &dp_controller0 {
> >>>      phys = <&dp_phy0 PHY_EDP>;
> >>> };
> >>>
> >>> &dp_controller1 {
> >>>      phys = <&dp_phy1 PHY_DP>;
> >>> };
> >>> ------------------
> >>>
> >>> as opposed to:
> >>>
> >>> --- device.dts ---
> >>> &dp_phy0 {
> >>>      phy-type <PHY_EDP>;
> >>> };
> >>>
> >>> &dp_phy1 {
> >>>      phy-type = <PHY_DP>;
> >>> };
> >>> ------------------
> >>
> >> Which is exactly what I proposed/wanted to see.
> >>
> >>>
> >>> i.e., we would be saying "this board is connected to this phy
> >>> instead" vs "this phy is of this type on this board".
> >>>
> >>> While none of them really fit the "same hw, different config"
> >>> situation, I'd vote for the latter one being closer to the
> >>> truth
> >>
> >> Then maybe I miss the bigger picture, but commit msg clearly says:
> >> "multiple PHYs that can work in both eDP or DP mode"
> >>
> >> If this is not the case, describe the hardware correctly in the commit
> >> msg, so people will not ask stupid questions...
> >
> > There are multiple PHYs (each of them at its own address space). Each
> > of the PHYs in question can be used either for the DisplayPort output
> > (directly or through the USB-C) or to drive the eDP panel.
> >
> > Same applies to the displayport-controller. It can either drive the DP
> > or eDP output, hardware-wise it is the same.
>
> Therefore what I proposed was correct - the block which uses the phy
> configures its mode. Because this part:
>   "this phy is of this type on this board".
> is not true. The phy is both types.

But hopefully you don't mean using #phy-cells here. There are no
sub-PHYs or anything like that.

-- 
With best wishes
Dmitry