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Message-ID: <5a8095e6-b6a6-4d11-b006-31519e8d8622@linaro.org>
Date: Fri, 15 Dec 2023 11:53:28 +0100
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Subject: Re: [PATCH v2 5/5] dt-bindings: net: ipq4019-mdio: Document ipq5332
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To: Jie Luo <quic_luoj@quicinc.com>, Conor Dooley <conor@kernel.org>
Cc: agross@kernel.org, andersson@kernel.org, konrad.dybcio@linaro.org,
 davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
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 <20231212115151.20016-6-quic_luoj@quicinc.com>
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From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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In-Reply-To: <7bae46fd-63fd-4b86-9a56-73052cf0ea95@quicinc.com>
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On 15/12/2023 11:40, Jie Luo wrote:
> 
> 
> On 12/15/2023 6:37 PM, Krzysztof Kozlowski wrote:
>> On 15/12/2023 11:33, Jie Luo wrote:
>>>>>>>>>>> +  cmn-reference-clock:
>>>>>>>>>>> +    oneOf:
>>>>>>>>>>> +      - items:
>>>>>>>>>>> +          - enum:
>>>>>>>>>>> +              - 0   # CMN PLL reference internal 48MHZ
>>>>>>>>>>> +              - 1   # CMN PLL reference external 25MHZ
>>>>>>>>>>> +              - 2   # CMN PLL reference external 31250KHZ
>>>>>>>>>>> +              - 3   # CMN PLL reference external 40MHZ
>>>>>>>>>>> +              - 4   # CMN PLL reference external 48MHZ
>>>>>>>>>>> +              - 5   # CMN PLL reference external 50MHZ
>>>>>>>>>>> +              - 6   # CMN PLL reference internal 96MHZ
>>>>>>>>>>
>>>>>>>>>> Why is this not represented by an element of the clocks property?
>>>>>>>>>
>>>>>>>>> This property is for the reference clock source selection of CMN PLL,
>>>>>>>>> CMN PLL generates the different clock rates for the different Ethernet
>>>>>>>>> blocks, this CMN PLL configuration is not located in the GCC, so the
>>>>>>>>> clock framework can't be used, which is the general hardware register
>>>>>>>>> instead of RCG register for GCC.
>>>>>>>>
>>>>>>>> I don't see how the clock being provided by the "GCC" (whatever that is)
>>>>>>>> or by some other clock controller or fixed clock makes a difference.
>>>>>>>> Why can't the other clock provider be represented in the devicetree?
>>>>>>>>
>>>>>>>
>>>>>>> cmn-reference-clock is for selecting the reference clock source for the
>>>>>>> whole Ethernet block, which is just the standalone configure register.
>>>>>>
>>>>>> Sure, you are aware though that all clocks are just configure registers?
>>>>>>
>>>>>> Which clocks are these mentioned in the property? From where do they come?
>>>>>>
>>>>>> Anyway, property is in existing form is not correct - this is not a
>>>>>> generic property.
>>>>>>
>>>>>
>>>>> This property cmn-reference-clock is just the hardware register
>>>>> configuration, since the different IPQ platform needs to select
>>>>> the different reference clock source for the CMN PLL block that
>>>>> provides the various clock outputs to the all kinds of Ethernet
>>>>> devices, which is not from GCC provider.
>>>>
>>>> AGAIN: where do the clocks come from? Which device generates them?
>>>
>>> Oh, OK, the reference clock is from wifi that provides 48MHZ to
>>> Ethernet block.
>>
>> Then WiFi should be providing you the clock and this device should be
>> clock consumer, right?
> 
> Yes, wifi provides 48MHz clock to CMM PLL block, there is no GCC
> for this 48MHZ clock output, it is the hardware PIN connection.

All clocks are some hardware pin connections.

Best regards,
Krzysztof