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 13:20:58 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...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 08/12/2023 13:17, Dmitry Baryshkov wrote:
>>>>>> 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.

I am exactly talking about phy-cells. Look at first example from Abel's
code.

Best regards,
Krzysztof