linux-kernel - Re: [PATCH 1/3] dt-bindings: interconnect: add clocks property to enable QoS on sa8775p

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Message-ID: <fdbcb092-a6bc-4da4-b7ea-1954b56f5d74@oss.qualcomm.com>
Date: Fri, 29 Aug 2025 01:36:08 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Odelu Kukatla <odelu.kukatla@....qualcomm.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Georgi Djakov <djakov@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Tipton <mike.tipton@....qualcomm.com>
Subject: Re: [PATCH 1/3] dt-bindings: interconnect: add clocks property to
 enable QoS on sa8775p

On 28/08/2025 21:16, Odelu Kukatla wrote:
> 
> 
> On 8/24/2025 2:38 PM, Krzysztof Kozlowski wrote:
>> On 20/08/2025 10:51, Odelu Kukatla wrote:
>>>
>>>
>>> On 8/13/2025 11:32 AM, Krzysztof Kozlowski wrote:
>>>> On 13/08/2025 07:55, Odelu Kukatla wrote:
>>>>>
>>>>>
>>>>> On 8/12/2025 3:47 PM, Krzysztof Kozlowski wrote:
>>>>>> On 08/08/2025 16:02, Odelu Kukatla wrote:
>>>>>>> Add reg and clocks properties to enable the clocks required
>>>>>>> for accessing QoS configuration.
>>>>>>
>>>>>>
>>>>>> Nothing here explains why EXISTING hardware is being changed. I also
>>>>>> remember big discussions and big confusing patches regarding sa8775p
>>>>>> (its rename, dropping/changing all providers), and this patch feels like
>>>>>> pieces of it without proper justification.
>>>>>>
>>>>> Thanks for the review.
>>>>> I have added description in cover letter, i will add here as well in next revision.> And this is hidden ABI break, no justification, no mentioning either.
>>>>>> Again we are discussing basics of ABI breaking patches?
>>>>>>
>>>>> If you are talking ABI break if we load old DT which may lead to crash, we have .qos_requires_clocks flag which takes care of skipping QoS if required clocks are not enabled.we have addressed this issue through https://lore.kernel.org/all/20240704125515.22194-1-quic_okukatla@quicinc.com/
>>>>
>>>> Format your emails correctly, it's difficult to read.
>>>>
>>>> Your binding did not require reg and clocks. Now it requires reg and
>>>> clocks. This is called ABI break.
>>>>
>>>> Please follow Qualcomm extensive upstreaming guide, it explains this,
>>>> doesn't it? Or follow writing bindings...
>>>>
>>>
>>> Thanks for your review and guidance.
>>>
>>> I agree that adding reg and clocks properties to existing bindings is an
>>> ABI break. The sa8775p is a relatively older platform, and when the
>>> interconnect provider driver was initially upstreamed, QoS configuration
>>> support was not available in the framework. As a result, QoS was not
>>> enabled at that time.
>>
>>
>> That's irrelevant reason. Writing bindings since long time ask pretty
>> clearly to describe hardware completely, regardless whether Linux
>> supports this or not.
>>
>> It does not matter if you enable QoS or not.
>>
> I agree with you. Ideally, the bindings should have described the
> hardware fully from the beginning. However, this was not done at the
> time of initial upstreaming, and the driver was contributed by someone
> from the community. I’m working now to improve the binding by adding the
> missing pieces to support QoS configuration.


Well, no. The driver was crontributed by:

commit 3655a63f9661b1fff313d8795200ff420282a87b
Author: Shazad Hussain <quic_shazhuss@...cinc.com>
Date:   Wed Jan 18 15:08:25 2023 +0100

     interconnect: qcom: add a driver for sa8775p

That's definitely not 'someone from the community'.

-- 
With best wishes
Dmitry