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

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Message-ID: <855d7daa-45d1-d6d8-32bd-51778cf58392@linaro.org>
Date:   Fri, 8 Apr 2022 10:17:26 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Johnson Wang <johnson.wang@...iatek.com>, cw00.choi@...sung.com,
        krzk+dt@...nel.org, robh+dt@...nel.org, kyungmin.park@...sung.com
Cc:     khilman@...nel.org, 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

On 08/04/2022 07:21, Johnson Wang wrote:
> Add devicetree binding of mtk cci devfreq on MediaTek SoC.
> 

Thank you for your patch. There is something to discuss/improve.

> Signed-off-by: Johnson Wang <johnson.wang@...iatek.com>
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> ---
>  .../devicetree/bindings/devfreq/mtk-cci.yaml  | 72 +++++++++++++++++++
>  1 file changed, 72 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/devfreq/mtk-cci.yaml

Filename with vendor prefix, so something like:

mediatek,cci.yaml

Also please put it in the "interconnect" directory.

> 
> diff --git a/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml b/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml
> new file mode 100644
> index 000000000000..ef4ea951025c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml
> @@ -0,0 +1,72 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/devfreq/mtk-cci.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: MediaTek Cache Coherent Interconnect (CCI) frequency and voltage scaling
> +
> +maintainers:
> +  - Jia-Wei Chang <jia-wei.chang@...iatek.com>
> +
> +description: |
> +  MediaTek Cache Coherent Interconnect (CCI) uses the software devfreq module

Do not reference software implementation (devfreq).

> +  to scale the clock frequency and adjust the voltage. MediaTek CCI shares
> +  the same power supplies with CPU, so the scheduling involves with CPUfreq.

The same - cpufreq.

Instead, focus on the hardware, what do you describe here?

> +
> +properties:
> +  compatible:
> +    enum:
> +      - mediatek,mt8183-cci
> +      - mediatek,mt8186-cci
> +
> +  clocks:
> +    items:
> +      - description:
> +          The multiplexer for clock input of CPU cluster.
> +      - description:
> +          A parent of "cpu" clock which is used as an intermediate clock source
> +          when the original CPU is under transition and not stable yet.
> +
> +  clock-names:
> +    items:
> +      - const: cci
> +      - const: intermediate
> +
> +  operating-points-v2:
> +    description:
> +      For details, please refer to
> +      Documentation/devicetree/bindings/opp/opp-v2.yaml

No need for description. Just "operating-points-v2: true".

"opp-table:true" could stay. My previous comment about its removal was a
wrong advice, because opp-table is used for a table being a children of
this device node.

Best regards,
Krzysztof