linux-kernel - Re: [PATCH v2 1/2] dt-bindings: devfreq: mediatek: Add mtk cci devfreq dt-bindings

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Date:   Thu, 14 Apr 2022 14:55:49 -0700
From:   Kevin Hilman <khilman@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Johnson Wang <johnson.wang@...iatek.com>,
        cw00.choi@...sung.com, krzk+dt@...nel.org, robh+dt@...nel.org,
        kyungmin.park@...sung.com
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, jia-wei.chang@...iatek.com,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2 1/2] dt-bindings: devfreq: mediatek: Add mtk cci
 devfreq dt-bindings

Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> writes:

> On 11/04/2022 14:10, Johnson Wang wrote:
>>> Also please put it in the "interconnect" directory.
>>>
>> 
>> I don't really know about "interconnect".
>> However, it looks like a Linux framework about data transfer and "NoC".
>> 
>> While this cci driver is more like a power managment which is
>> responsible for adjusting voltages and frequencies.
>> In my opinion, "devfreq" should be more suitable.
>> 
>> Please correct me if my understanding is wrong.
>
> devfreq is a Linux mechanism, not a real device/hardware. We try to put
> the bindings in directories/subsystems matching the hardware, therefore
> devfreq is not appropriate.
>
> Whether interconnect - or other subsystem - is appropriate, I am not
> sure. To me this looks exactly like bus bandwidth management and you
> even use "interconnect" in several places. So interconnect matches.

I agree with Krzysztof that "interconnect" is the right place.

I'm pretty sure CCI stands for "cache coherent interconnect".  At least
that's what it means for the Arm IP.  The Mediatek IP being described
here certainly seems like the same thing.  It's just that the only
aspects being described (so far) are the DVFS parts.  Even so, I still
think it belongs in "interconnect"

Kevin