linux-kernel - Re: [PATCH 1/4] dt-bindings: clock: qcom: Add common PLL clock controller for IPQ SoC

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Message-ID: <5e84204f-ff47-427c-a077-4e68773ad20e@quicinc.com>
Date: Wed, 14 Aug 2024 23:13:58 +0800
From: Jie Luo <quic_luoj@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        "Stephen
 Boyd" <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Catalin Marinas
	<catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Konrad Dybcio
	<konradybcio@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <quic_kkumarcs@...cinc.com>,
        <quic_suruchia@...cinc.com>, <quic_pavir@...cinc.com>,
        <quic_linchen@...cinc.com>, <quic_leiwei@...cinc.com>
Subject: Re: [PATCH 1/4] dt-bindings: clock: qcom: Add common PLL clock
 controller for IPQ SoC



On 8/10/2024 7:30 PM, Krzysztof Kozlowski wrote:
> On 09/08/2024 15:01, Jie Luo wrote:
>>>> +  clock-names:
>>>> +    items:
>>>> +      - const: ref
>>>> +      - const: ahb
>>>> +      - const: sys
>>>> +
>>>> +  clock-output-names:
>>>> +    items:
>>>> +      - const: ppe-353mhz
>>>> +      - const: eth0-50mhz
>>>> +      - const: eth1-50mhz
>>>> +      - const: eth2-50mhz
>>>> +      - const: eth-25mhz
>>>
>>> Drop entire property. If the names are fixed, what's the point of having
>>> it in DTS? There is no.
>>
>> We had added the output names here for the reasons below. Can you please
>> let us know your suggestion whether keeping these here is fine?
>>
>> 1.) These output clocks are used as input reference clocks to other
>> consumer blocks. For example, an on-board Ethernet PHY device may be
>> wired to receive a specific clock from the above output clocks as
>> reference clock input, and hence the PHY's DTS node would need to
>> reference a particular index in this output clock array.
>>
>> Without these output clocks being made available in this DTS, the PHY
>> driver in above case would not know the clock specifier to access the
>> handle for the desired input clock.
> 
> That's not true. clock-output-names do not have anything to do with
> clock specifier.
> 
>>
>> 2.) One of the suggestions from the internal code review with Linaro was
>> to name the output clocks specifically based on rate and destination
>> (Ex: 'ppe-353mhz' for fixed rate 353 MHZ output clock connected to
>> Packet Process Engine block), so that the dt-bindings describe the
>> input/output clocks clearly.
> 
> Again, that's unrelated. None of above points address my concern. It's
> like you talk about some entirely different topic. Again:
> clock-output-names have nothing to do with what you want to achieve here.

OK, understand. I will drop this property "clock-output-names" from the
bindings and DTS. These names will instead be defined in the driver. For
the consumer clock device DTS nodes that need to reference these output
clocks, I will export the clock specifiers for these output clocks from
a header file. Hope this approach is fine.

> 
> Best regards,
> Krzysztof
>