linux-kernel - Re: [PATCH v3 1/3] dt-bindings: phy: qcom,qmp: Add PCIe qcom,refclk-always-on property

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Message-ID: <f844cd1e-7e4f-4836-bc9a-2e1ed13f064f@linaro.org>
Date:   Fri, 1 Dec 2023 13:10:48 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.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>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_vpernami@...cinc.com, quic_parass@...cinc.com
Subject: Re: [PATCH v3 1/3] dt-bindings: phy: qcom,qmp: Add PCIe
 qcom,refclk-always-on property

On 01/12/2023 12:10, Manivannan Sadhasivam wrote:
> On Fri, Dec 01, 2023 at 09:01:43AM +0100, Krzysztof Kozlowski wrote:
>> On 01/12/2023 07:07, Manivannan Sadhasivam wrote:
>>> On Tue, Nov 28, 2023 at 02:49:18PM +0530, Krishna Chaitanya Chundru wrote:
>>>>
>>>> On 11/28/2023 2:26 PM, Krzysztof Kozlowski wrote:
>>>>> On 27/11/2023 13:13, Krishna chaitanya chundru wrote:
>>>>>> Document qcom,refclk-always-on property which is needed in some platforms
>>>>>> to supply refclk even in PCIe low power states.
>>>>>>
>>>>>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>>>>>> ---
>>>>>>   .../devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml        | 7 +++++++
>>>>>>   1 file changed, 7 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
>>>>>> index 2c3d6553a7ba..c747c9f35795 100644
>>>>>> --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
>>>>>> +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
>>>>>> @@ -93,6 +93,13 @@ properties:
>>>>>>     "#phy-cells":
>>>>>>       const: 0
>>>>>> +  qcom,refclk-always-on:
>>>>>> +    type: boolean
>>>>>> +    description: In some platform where PCIe switch is connected, pcie switch due to some design
>>>>> You received a comment to use proper wrapping: 80. Please implement it.
>>>> I will update this.
>>>>>> +      limitation fails to propage clkreq signal to the host and due to that host will not send
>>>>>> +      refclk, which  results in linkdown in L1.2 or L1.1 exit initiated by EP.
>>>>>> +      This property if set keeps refclk always on even in Low power states.
>>>>> The property name suggests that's the state of hardware - refclk is
>>>>> always on. Description suggests you want to instruct OS to do something.
>>>>>
>>>>> Again, third time (once from Bjorn, once from Dmitry), rephrase property
>>>>> name and description to describe the hardware issue. I see description
>>>>> improved, but not the property name. Again in the end of description you
>>>>
>>>> Both bjorn and Dmitry gave comments to change the description only, and not
>>>> the property name,
>>>>
>>>> correct if I am wrong.
>>>>
>>>>> say what Linux should do. Bindings do not describe Linux OS.
>>>>
>>>> I will remove the last line in the next patch.
>>>>
>>>
>>> You should name the property as, "qcom,keep-refclk-always-on"
>>
>> Keep the clock by who? By driver? Then not, property should describe
>> physical phenomena or hardware issue being fixed here, not what driver
>> should do.
>>
> 
> This property indeed fixes the hardware issue (though in board level) and I see
> a plenty of properties similar to this one instructing the OS to keep some
> resource ON to workaround hardware issues. So they are all wrong?

What I said before:
"Again, third time (once from Bjorn, once from Dmitry), rephrase
property name and description to describe the hardware issue. I see
description improved, but not the property name. Again in the end of
description you say what Linux should do. Bindings do not describe Linux
OS."


Best regards,
Krzysztof