linux-kernel - Re: [PATCH 1/4] dt-bindings: cpufreq: mediatek: transform cpufreq-mediatek into yaml

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Message-ID: <96a823a2-f3b6-9fb7-c9d6-f1315f6056fd@kernel.org>
Date:   Thu, 24 Mar 2022 11:33:47 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Jia-Wei Chang <jia-wei.chang@...iatek.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, fan.chen@...iatek.com,
        louis.yu@...iatek.com, roger.lu@...iatek.com,
        Allen-yy.Lin@...iatek.com,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        hsinyi@...gle.com,
        Jia-Wei Chang <jia-wei.chang@...iatek.corp-partner.google.com>
Subject: Re: [PATCH 1/4] dt-bindings: cpufreq: mediatek: transform
 cpufreq-mediatek into yaml

On 24/03/2022 10:38, Jia-Wei Chang wrote:
>>
>>>
>>> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-
>>> mediatek.yaml b/Documentation/devicetree/bindings/cpufreq/cpufreq-
>>> mediatek.yaml
>>> new file mode 100644
>>> index 000000000000..584946eb3790
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-
>>> mediatek.yaml
>>> @@ -0,0 +1,131 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: 
>>> https://urldefense.com/v3/__http://devicetree.org/schemas/cpufreq/cpufreq-mediatek.yaml*__;Iw!!CTRNKA9wMg0ARbw!xbKG4TgD0MRpMLyGJVBZEGpZFrNOclrcxOCx_APKo5Nmg8nF2x5PcBdE0unvL2NdpChkMA$
>>>  
>>> +$schema: 
>>> https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!xbKG4TgD0MRpMLyGJVBZEGpZFrNOclrcxOCx_APKo5Nmg8nF2x5PcBdE0unvL2O8T_oxCQ$
>>>  
>>> +
>>> +title: Mediatek CPUFREQ driver Device Tree Bindings
>>
>> Please remove "driver Device Tree Bindings" because the title should
>> describe the hardware. Therefore it could be something like "Mediatek
>> SoC CPU frequency and voltage scaling".
> 
> Thanks for your suggestion of title.
> Or should I use the origin title "Binding for MediaTek's CPUFreq
> driver"?

Mediatek CPUFREQ
or
Mediatek CPU frequency scaling

> 
>>
>> How is it related to cpufreq-mediatek-hw.yaml? The names/title look
>> unfortunately too similar.
> 
> No, mediatek-cpufreq is performing in kernel driver rather than on
> hardware.
> On the other hand, mediatek-cpufreq-hw is performing on hardware.
> That's why "hw" is present in its name.

Unfortunately, I do not get it. The bindings are only about hardware, so
how bindings could be about CPU frequency scaling not in hardware?

> 
>>
>> In general this does not look like proper bindings (see also below
>> lack
>> of compatible). Bindings describe the hardware, so what is exactly
>> the
>> hardware here?
> 
> Except for SoC, there's no requirement of hardware binding for
> mediatek-cpufreq.
> mediatek-cpufreq recognizes the compatible of Mediatek SoC while
> probing.

What is the hardware here? If there is no requirement for bindings for
mediate-cpufreq, why do we have this patch here?

> 
>>
>>> +
>>> +maintainers:
>>> +  - Jia-Wei Chang <jia-wei.chang@...iatek.com>
>>> +
>>> +description: |
>>> +  CPUFREQ is used for scaling clock frequency of CPUs.
>>> +  The module cooperates with CCI DEVFREQ to manage frequency for
>>> some Mediatek
>>> +  SoCs.
>>> +
>>> +properties:
>>
>> How is this schema going to be applied? I don't see here select
>> neither
>> compatible.
> 
> As mentioned above, only compatible of SoC is required for mediatek-
> cpufreq.

It does not answer my questions. How the schema is going to be applied?


Best regards,
Krzysztof