linux-kernel - Re: [PATCH v3 05/10] dt-bindings: clock: ipq9574: Rename NSS CC source clocks to drop rate

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Message-ID: <a383041e-7b70-4ffd-ae15-2412b2f83770@oss.qualcomm.com>
Date: Fri, 18 Jul 2025 11:28:12 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Luo Jie <quic_luoj@...cinc.com>, Rob Herring <robh@...nel.org>
Cc: Georgi Djakov <djakov@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd
 <sboyd@...nel.org>, Anusha Rao <quic_anusha@...cinc.com>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        quic_kkumarcs@...cinc.com, quic_linchen@...cinc.com,
        quic_leiwei@...cinc.com, quic_pavir@...cinc.com,
        quic_suruchia@...cinc.com
Subject: Re: [PATCH v3 05/10] dt-bindings: clock: ipq9574: Rename NSS CC
 source clocks to drop rate

On 7/18/25 11:12 AM, Luo Jie wrote:
> 
> 
> On 7/11/2025 8:15 PM, Konrad Dybcio wrote:
>> On 7/11/25 12:54 AM, Rob Herring wrote:
>>> On Thu, Jul 10, 2025 at 08:28:13PM +0800, Luo Jie wrote:
>>>> Drop the clock rate suffix from the NSS Clock Controller clock names for
>>>> PPE and NSS clocks. A generic name allows for easier extension of support
>>>> to additional SoCs that utilize same hardware design.
>>>
>>> This is an ABI change. You must state that here and provide a reason the
>>> change is okay (assuming it is). Otherwise, you are stuck with the name
>>> even if not optimal.
>>
>> The reason here seems to be simplifying the YAML.. which is not a good
>> reason really..
>>
>> I would instead suggest keeping the clocks list as-is for ipq9574 (this
>> existing case), whereas improving it for any new additions
>>
>> Konrad
> 
> Thanks Rob and Konrad for the comments.
> 
> "nss_1200" and "nss" refer to the same clock pin on different SoC.
> As per Krzystof's previous comment on V2, including the frequency
> as a suffix in the clock name is not required, since only the
> frequencies vary across different IPQ SoCs, while the source clock
> pins for 'PPE' and 'NSS' clocks are the same. Hence this ABI change
> was deemed necessary.
> 
> By removing the frequency suffix, the device tree bindings becomes
> more flexible and easier to extend for supporting new hardware
> variants in the future.
> 
> Impact due to this ABI change: The NSS clock controller node is only
> enabled for the IPQ9574 DTS. In this patch series, the corresponding
> DTS changes for IPQ9574 are also included to align with this ABI
> change.

The point of an ABI is to keep exposing the same interface without
any change requirements, i.e. if a customer ships the DT from
torvalds/master in firmware and is not willing to update it, they
can no longer update the kernel without a workaround.

> Please let me know if further clarification or adjustments are needed.

What we're asking for is that you don't alter the name on the
existing platform, but use a no-suffix version for the ones you
introduce going forward

i.e. (pseudo-YAML)

if:
  properties:
    compatible:
      - const: qcom,ipq9574-nsscc
then:
  properties:
    clock-names:
      items:
        - clockname_1200
else:
  properties:
    clock-names:
      items:
        - clockname # no suffix

Konrad