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

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Message-ID: <53f25764-41d6-491f-9397-988d3e672189@kernel.org>
Date: Sat, 10 Aug 2024 13:30:57 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jie Luo <quic_luoj@...cinc.com>, 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 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.

Best regards,
Krzysztof