linux-kernel - Re: [PATCH v3 3/3] arm64: qcom: sc7280: Move phy, perst to root port node

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Message-ID: <56eccdb0-c877-431d-9833-16254afa1a0c@oss.qualcomm.com>
Date: Tue, 10 Jun 2025 15:15:43 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Rob Herring
 <robh@...nel.org>,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski
 <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        cros-qcom-dts-watchers@...omium.org, linux-arm-msm@...r.kernel.org,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_vbadigan@...cinc.com,
        quic_mrana@...cinc.com
Subject: Re: [PATCH v3 3/3] arm64: qcom: sc7280: Move phy, perst to root port
 node

On 6/2/25 3:01 PM, Krzysztof Kozlowski wrote:
> On 08/05/2025 16:26, Konrad Dybcio wrote:
>> On 4/23/25 5:37 PM, Rob Herring wrote:
>>> On Sat, Apr 19, 2025 at 10:49:26AM +0530, Krishna Chaitanya Chundru wrote:
>>>> There are many places we agreed to move the wake and perst gpio's
>>>> and phy etc to the pcie root port node instead of bridge node[1].
>>>>
>>>> So move the phy, phy-names, wake-gpio's in the root port.
>>>> There is already reset-gpio defined for PERST# in pci-bus-common.yaml,
>>>> start using that property instead of perst-gpio.
>>>
>>> Moving the properties will break existing kernels. If that doesn't 
>>> matter for these platforms, say so in the commit msg.
>>
>> I don't think we generally guarantee *forward* dt compatibility though, no?
> We do not guarantee, comment was not about this, but we expect. This DTS
> is supposed and is used by other projects. There was entire complain
> last DT BoF about kernel breaking DTS users all the time.

Yeah I get it.. we're in a constant cycle of adding new components and
later coming to the conclusion that whoever came up with the initial
binding had no clue what they're doing..

That said, "absens carens".. if users or developers of other projects
don't speak up on LKML (which serves as the de facto public square for
DT development), we don't get any feedback to take into account when
making potentially breaking changes (that may have a good reason behind
them). We get a patch from OpenBSD people every now and then, but it's
a drop in the ocean.

Konrad