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

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Message-ID: <d1e3fede-0f75-4c00-a087-d04923000ae3@kernel.org>
Date: Wed, 11 Jun 2025 17:33:35 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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 11/06/2025 17:17, Konrad Dybcio wrote:
> On 6/11/25 8:36 AM, Krzysztof Kozlowski wrote:
>> On 10/06/2025 15:15, Konrad Dybcio wrote:
>>> 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.
>>>
>> I don't understand what you are commenting on. Do you reject what I
>> asked for?
> 
> If the general consensus among kernel PCIe folks will come down to what
> this patch does, I think it's fair to shift to a "correct" hw
> description, especially if this is a requirement to resolve a blocker
> on functionality (which the author didn't clarify whether is the case)

Again I do not see how this argues with my comment, so please clarify:
do you agree or disagree with my request?

Best regards,
Krzysztof