linux-kernel - Re: [PATCH v4 5/5] dt-bindings: net: ipq4019-mdio: Document ipq5332 platform

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Message-ID: <7ad0a344-4f24-4319-8f60-ed2521c21815@quicinc.com>
Date: Tue, 26 Dec 2023 21:14:02 +0800
From: Jie Luo <quic_luoj@...cinc.com>
To: Conor Dooley <conor@...nel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>
CC: <agross@...nel.org>, <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
        <robert.marko@...tura.hr>, <linux-arm-msm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_srichara@...cinc.com>
Subject: Re: [PATCH v4 5/5] dt-bindings: net: ipq4019-mdio: Document ipq5332
 platform



On 12/26/2023 8:21 PM, Conor Dooley wrote:
> On Tue, Dec 26, 2023 at 10:28:09AM +0100, Krzysztof Kozlowski wrote:
>> On 26/12/2023 08:25, Jie Luo wrote:
> 
>>>>> +  qcom,cmn-ref-clock-frequency:
>>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>>> +    enum:
>>>>> +      - 25000000
>>>>> +      - 31250000
>>>>> +      - 40000000
>>>>> +      - 48000000
>>>>> +      - 50000000
>>>>> +      - 96000000
>>>>> +    default: 48000000
>>>>> +    description: |
>>>>> +      The reference clock source of CMN PLL block is selectable, the
>>>>> +      reference clock source can be from wifi module or the external
>>>>> +      xtal, the reference clock frequency 48MHZ can be from internal
>>>>> +      wifi or the external xtal, if absent, the internal 48MHZ is used,
>>>>> +      if the 48MHZ is specified, which means the external 48Mhz is used.
>>>>
>>>> This does not resolve mine and Conor's concerns from previous version.
>>>> External clocks are defined as clock inputs.
>>>
>>> No matter the external or internal reference clock, they are the clock
>>> source selection for CMN, there are only 48MHZ can be external or
>>> internal, other clocks have the different clock rate, so the internal
>>> 48MHZ reference clock can be implied when the
>>> "qcom,cmn-ref-clock-frequency" is not defined, which is suggested by
>>> Conor in the previous
>>> comments.
>>
>> I don't think he proposed it, but maybe I missed some message (care to
>> point me to his message where he agreed on usage of
>> qcom,cmn-ref-clock-frequency?). I am pretty sure we both stayed on the
>> same page, that the presence of clocks defines choice of internal clock.
>> This property should go away.
> 
> Exactly, I wanted this property to be removed. My suggestion was about
> defaulting to the internal clock when the "clocks" property did not
> contain the cmn ref clock.

There are two internal reference clock sources 48MHZ and 96MHZ.
The 96MHZ is used on ipq5018 currently as i said in the previous
message, but it is also possible to used on ipq9574 per double checked,
since the possible reference clock source should be kept as configurable
and the clock source should not be limited on the specific IPQ platform,
since the clock source is configurable, the different clock source maybe
required by the different board design.

As description above, the reference clock source has the different clock
rate except the 48MHZ, so it can imply that the internal 48MHZ used when
the property is absent.

> 
>> It is tiring to keep discussing this.
> 
> Yup.
>