linux-kernel - Re: [PATCH v5 02/10] dt-bindings: phy: qcom,qmp-usb: Add Glymur USB UNI PHY compatible

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Message-ID: <99ab26d3-eb44-401d-8a7c-1d9efd2a1a10@kernel.org>
Date: Tue, 14 Oct 2025 06:36:21 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Wesley Cheng <wesley.cheng@....qualcomm.com>, krzk+dt@...nel.org,
 conor+dt@...nel.org, konrad.dybcio@....qualcomm.com,
 dmitry.baryshkov@....qualcomm.com, kishon@...nel.org, vkoul@...nel.org,
 gregkh@...uxfoundation.org, robh@...nel.org
Cc: linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
 linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 02/10] dt-bindings: phy: qcom,qmp-usb: Add Glymur USB
 UNI PHY compatible

On 14/10/2025 03:16, Wesley Cheng wrote:
>>>
>>>>>> +          maxItems: 5
>>>>>> +        clock-names:
>>>>>> +          items:
>>>>>> +            - const: aux
>>>>>> +            - const: clkref
>>>>>> +            - const: ref
>>>>>
>>>>> What is the difference between these two? Which block INPUTs
>>>>> (important!) they represent?
>>>>>
>>>>
>>>> clkref is the TCSR reference clock switch, and the ref is the actual CXO
>>>> handle.
>>
>>
>> Then this should be named somehow differently. CXO is clock. Reference
>> clock is clock... To me it feels like you are describing the same clock,
>> just missing some gate in TCSR. But in case these are not the same
>> clocks, you need to name it accurately.
>>
> 
> Technically its all handling the same clock branch (CXO), we have the 
> TCSR clkref register that allows us to gate the CXO to the USB PHY, as 


Ah, exactly. Then clkref is not a clock. You need rather proper clock
hierarchy.

> CXO is shared across several HW blocks, so it allows us to properly 
> powerdown the PHY even though other clients are voting for CXO on.  Then 
> we obviously have to remove our vote to the overall CXO, so that it can 
> potentially be shutdown.
> 
> Maybe we can rename it to "clkref" for the CXO handle and 
> "clkref_switch" for the TCSRCC handle?

Naming is better, but it is still not correct. This is not independent
clock signal. It is the same clock.


Best regards,
Krzysztof