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 12:45:19 +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 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.

Best regards,
Krzysztof