linux-kernel - Re: [PATCH v3 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping

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Message-ID: <8fd7c872-fadb-5dc2-6bc1-5b59a9a3b133@collabora.com>
Date:   Thu, 6 Oct 2022 14:33:59 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Johnson Wang (王聖鑫) 
        <Johnson.Wang@...iatek.com>, "robh@...nel.org" <robh@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Kuan-Hsin Lee (李冠新) 
        <Kuan-Hsin.Lee@...iatek.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Yu-Chang Wang (王煜樟) 
        <Yu-Chang.Wang@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        Edward-JW Yang (楊哲維) 
        <Edward-JW.Yang@...iatek.com>
Subject: Re: [PATCH v3 2/4] dt-bindings: arm: mediatek: Add new bindings of
 MediaTek frequency hopping

Il 06/10/22 13:23, Johnson Wang (王聖鑫) ha scritto:
> On Fri, 2022-09-30 at 14:07 -0500, Rob Herring wrote:
>> On Thu, Sep 29, 2022 at 03:07:49PM +0200, AngeloGioacchino Del Regno
>> wrote:
>>> Il 29/09/22 13:46, Johnson Wang ha scritto:
>>>> Add the new binding documentation for MediaTek frequency hopping
>>>> and spread spectrum clocking control.
>>>>
>>>> Co-developed-by: Edward-JW Yang <edward-jw.yang@...iatek.com>
>>>> Signed-off-by: Edward-JW Yang <edward-jw.yang@...iatek.com>
>>>> Signed-off-by: Johnson Wang <johnson.wang@...iatek.com>
>>>> ---
>>>>    .../arm/mediatek/mediatek,mt8186-fhctl.yaml   | 53
>>>> +++++++++++++++++++
>>>>    1 file changed, 53 insertions(+)
>>>>    create mode 100644
>>>> Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
>>>> fhctl.yaml
>>>>
>>>> diff --git
>>>> a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
>>>> fhctl.yaml
>>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
>>>> fhctl.yaml
>>>> new file mode 100644
>>>> index 000000000000..258dff7ce6bc
>>>> --- /dev/null
>>>> +++
>>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mt8186-
>>>> fhctl.yaml
>>>> @@ -0,0 +1,53 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id:
>>>> https://urldefense.com/v3/__http://devicetree.org/schemas/arm/mediatek/mediatek,mt8186-fhctl.yaml*__;Iw!!CTRNKA9wMg0ARbw!xVt73f8PaQKph8n0ffGHHmQIxdzooUtGr0xDNVqy_6V0vwcs5k-FLrmkB3PZupSu1ciC$
>>>>   
>>>> +$schema:
>>>> https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!xVt73f8PaQKph8n0ffGHHmQIxdzooUtGr0xDNVqy_6V0vwcs5k-FLrmkB3PZulXwBACk$
>>>>   
>>>> +
>>>> +title: MediaTek frequency hopping and spread spectrum clocking
>>>> control
>>>> +
>>>> +maintainers:
>>>> +  - Edward-JW Yang <edward-jw.yang@...iatek.com>
>>>> +
>>>> +description: |
>>>> +  Frequency hopping control (FHCTL) is a piece of hardware that
>>>> control
>>>> +  some PLLs to adopt "hopping" mechanism to adjust their
>>>> frequency.
>>>> +  Spread spectrum clocking (SSC) is another function provided by
>>>> this hardware.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    const: mediatek,mt8186-fhctl
>>>> +
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  clocks:
>>>> +    description: Phandles of the PLL with FHCTL hardware
>>>> capability.
>>>> +    minItems: 1
>>>> +    maxItems: 30
>>>> +
>>>> +  mediatek,hopping-ssc-percent:
>>>> +    description: The percentage of spread spectrum clocking for
>>>> one PLL.
>>>> +    minItems: 1
>>>> +    maxItems: 30
>>>> +    items:
>>>> +      default: 0
>>>> +      minimum: 0
>>>> +      maximum: 8
>>>> +
>>>> +required:
>>>> +  - compatible
>>>> +  - reg
>>>> +  - clocks
>>>> +
>>>> +additionalProperties: false
>>>> +
>>>> +examples:
>>>> +  - |
>>>> +    #include <dt-bindings/clock/mt8186-clk.h>
>>>> +    fhctl: fhctl@...0ce00 {
>>>> +        compatible = "mediatek,mt8186-fhctl";
>>>> +        reg = <0x1000c000 0xe00>;
>>>> +        clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
>>>> +        mediatek,hopping-ssc-percent = <3>;
>>>> +    };
>>>
>>>
>>> .... a more realistic example:
>>
>> One or 2 cells is really outside the scope of the binding as either
>> is
>> valid. If the parent bus only has 32-bits of address space, there's
>> little reason to use 2 cells.
>>
> 
> Hi Rob,
> 
> Thanks for the explanation.
> 
> Then I will keep this example the same in the next version.

That was just to have it 1:1 with how it'll be written in the devicetree....
....in any case, Johnson, there's a discrepancy in the iospace:
1000ce00 vs 0c1000c000 - that has to be fixed anyway.

Cheers,
Angelo

> 
> BRs,
> Johnson Wang
>>>
>>>      #include <dt-bindings/clock/mt8186-clk.h>
>>>
>>>      soc {
>>>          #address-cells = <2>;
>>>          #size-cells = <2>;
>>>
>>>          fhctl: fhctl@...0ce00 {
>>>              compatible = "mediatek,mt8186-fhctl";
>>>              reg = <0 0x1000c000 0 0xe00>;
>>>              clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
>>>              mediatek,hopping-ssc-percent = <3>;
>>>          };
>>>      };
>>>
>>> After which...
>>>
>>> Reviewed-by: AngeloGioacchino Del Regno <
>>> angelogioacchino.delregno@...labora.com>
>>>