linux-kernel - Re: [PATCH 1/3] dt-bindings: devfreq: mediatek: add mtk cci devfreq dt-bindings

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Message-ID: <13482b1b4244df5c0c0a4d6a60cdb2a7ba88500a.camel@mediatek.com>
Date:   Thu, 24 Mar 2022 20:11:08 +0800
From:   Jia-Wei Chang <jia-wei.chang@...iatek.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
CC:     <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.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 1/3] dt-bindings: devfreq: mediatek: add mtk cci devfreq
 dt-bindings

Dear Krzysztof,

Thanks for your comments.
Pardon me for my late reply.

On Mon, 2022-03-07 at 22:42 +0100, Krzysztof Kozlowski wrote:
> On 07/03/2022 13:25, Tim Chang wrote:
> > add devicetree binding of mtk cci devfreq on MediaTek SoC.
> 
> Start with capital letter.

Sure, I will update it for the whole series in next version.

> 
> > 
> > Signed-off-by: Jia-Wei Chang <
> > jia-wei.chang@...iatek.corp-partner.google.com>
> 
> This does not match your From. Please fix this in all your
> submissions.

Sure, I will update it for the whole series in next version.

> 
> > ---
> >  .../devicetree/bindings/devfreq/mtk-cci.yaml  | 73
> > +++++++++++++++++++
> >  1 file changed, 73 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/devfreq/mtk-
> > cci.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml 
> > b/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml
> > new file mode 100644
> > index 000000000000..e64ac4c56758
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/devfreq/mtk-cci.yaml
> > @@ -0,0 +1,73 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: 
> > https://urldefense.com/v3/__http://devicetree.org/schemas/devfreq/mtk-cci.yaml*__;Iw!!CTRNKA9wMg0ARbw!2apx_16V_XMrl28ae1aDO3-2WFga3xJiACU_40mgGydrumBmFuHcQFpW_LnX6DHny5Zpig$
> >  
> > +$schema: 
> > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!2apx_16V_XMrl28ae1aDO3-2WFga3xJiACU_40mgGydrumBmFuHcQFpW_LnX6DEPqkDN4g$
> >  
> > +
> > +title: Mediatek Cache Coherent Interconnect (CCI) Devfreq driver
> > Device Tree Bindings
> 
> Similarly to your other patches - the title describes hardware.
> Please
> fix it in all your submissions of all your series.

Sure, I will fix them in the next version.

> 
> Remove "driver Device Tree Bindings". "Devfreq" is Linuxism, so this
> maybe "bus frequency scaling"? Although later you call the device
> node
> as cci.

Should I use "Binding for MediaTek's Cache Coherent Interconnect (CCI)
frequency and voltage scaling" as new title?

> 
> > +
> > +maintainers:
> > +  - Jia-Wei Chang <jia-wei.chang@...iatek.com>
> > +
> > +description: |
> > +  This module is used to create CCI DEVFREQ.
> > +  The performance will depend on both CCI frequency and CPU
> > frequency.
> > +  For MT8186, CCI co-buck with Little core.
> > +  Contain CCI opp table for voltage and frequency scaling.
> 
> Half of this description (first and last sentence) does not describe
> the
> actual hardware. Please describe hardware, not driver.

Sure, I will fix it in the next version.

> 
> > +
> > +properties:
> > +  compatible:
> > +    const: "mediatek,mt8186-cci"
> 
> No need for quotes.

Sure, I will fix it in the next version.

> 
> > +
> > +  clocks:
> > +    items:
> > +      - description:
> > +          The first one is the multiplexer for clock input of CPU
> > cluster.
> > +      - description:
> > +          The other 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"
> 
> No need for quotes.

Sure, I will fix it in the next version.

> 
> > +
> > +  operating-points-v2:
> > +    description:
> > +      For details, please refer to
> > +      Documentation/devicetree/bindings/opp/opp-v2.yaml
> > +
> > +  opp-table: true
> 
> Same comments as your CPU freq bindings apply.

mtk-cci-devfreq is a new driver and its arch is same as mediatek-
cpufreq so that the properties of mtk-cci are refer to mediatek-cpufreq 
bindings.
operating-point-v2 is used to determine the voltage and frequency of
dvfs which is further utilized by mtk-cci-devfreq.

> 
> > +
> > +  proc-supply:
> > +    description:
> > +      Phandle of the regulator for CCI that provides the supply
> > voltage.
> > +
> > +  sram-supply:
> > +    description:
> > +      Phandle of the regulator for sram of CCI that provides the
> > supply
> > +      voltage. When present, the cci devfreq driver needs to do
> > +      "voltage tracking" to step by step scale up/down Vproc and
> > Vsram to fit
> > +      SoC specific needs. When absent, the voltage scaling flow is
> > handled by
> > +      hardware, hence no software "voltage tracking" is needed.
> > +
> > +required:
> > +  - compatible
> > +  - clocks
> > +  - clock-names
> > +  - operating-points-v2
> > +  - proc-supply
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/mt8186-clk.h>
> > +    cci: cci {
> 
> Node names should be generic and describe type of device. Are you
> sure
> this is a CCI? Maybe "interconnect" suits it better?

Yes, this is a CCI and it is generic type of device like CPU in my
opinion.
If my understanding is correct, CCI is more suitable.

> 
> > +      compatible = "mediatek,mt8186-cci";
> > +      clocks = <&mcusys CLK_MCU_ARMPLL_BUS_SEL>, <&apmixedsys
> > CLK_APMIXED_MAINPLL>;
> > +      clock-names = "cci", "intermediate";
> > +      operating-points-v2 = <&cci_opp>;
> > +      proc-supply = <&mt6358_vproc12_reg>;
> > +      sram-supply = <&mt6358_vsram_proc12_reg>;
> > +    };
> 
> 
> Best regards,
> Krzysztof