linux-kernel - Re: [PATCH 1/2] dt-bindings: clock: qcom,sm8450-videocc: Add minItems property

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Message-ID: <3d2e9354-40a5-4908-a6a6-cfc8afd4c702@quicinc.com>
Date: Mon, 23 Jun 2025 23:14:05 +0530
From: Jagadeesh Kona <quic_jkona@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Konrad Dybcio
	<konrad.dybcio@....qualcomm.com>
CC: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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>,
        Bryan O'Donoghue
	<bryan.odonoghue@...aro.org>,
        Vladimir Zapolskiy
	<vladimir.zapolskiy@...aro.org>,
        Ajit Pandey <quic_ajipan@...cinc.com>,
        "Imran Shaik" <quic_imrashai@...cinc.com>,
        Taniya Das
	<quic_tdas@...cinc.com>,
        "Satya Priya Kakitapalli"
	<quic_skakitap@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "kernel test robot" <lkp@...el.com>
Subject: Re: [PATCH 1/2] dt-bindings: clock: qcom,sm8450-videocc: Add minItems
 property



On 6/21/2025 3:04 AM, Dmitry Baryshkov wrote:
> On Fri, Jun 20, 2025 at 07:39:06PM +0200, Konrad Dybcio wrote:
>> On 6/20/25 7:56 AM, Krzysztof Kozlowski wrote:
>>> On 19/06/2025 12:20, Jagadeesh Kona wrote:
>>>>
>>>>
>>>> On 6/18/2025 11:56 AM, Krzysztof Kozlowski wrote:
>>>>> On 17/06/2025 21:07, Jagadeesh Kona wrote:
>>>>>> Add minItems as 1 for power-domains and required-opps properties
>>>>>> to allow this binding to be compatible with both single and multiple
>>>>>> power domains.
>>>>>
>>>>> This is your hardware, so you know how it works thus I expect here
>>>>> arguments why this is correct from the hardware point of view. Without
>>>>> this, it is impossible to judge whether this is a correct change.
>>>>>
>>>>> If I overlook this now, it will be used in discussions by other qcom
>>>>> engineers, so unfortunately you see, you need to prepare perfect commits
>>>>> now...
>>>>>
>>>>
>>>> These clk controllers mainly require MMCX power domain to be enabled to access
>>>> the clock registers. But to configure the cam & video PLLs in probe, an additional
>>>> MXC power domain also needs to be enabled.
>>>
>>>
>>> Then your patch is not correct. Anyway, you should explain the hardware
>>> in commit msg, why this domain is optional in the hardware.
>>>
>>>>
>>>> Since the initial DTS changes only added MMCX power domain, this change is required
>>>> to be backward compatible with older DTS and avoid ABI breakage as discussed in below
>>>> thread.
>>>
>>>
>>> So you send incorrect hardware description allowing something which will
>>> not work? Or how exactly?
>>

The initial videocc with single power domain works fine, but in that case the
PLL's work with default sub-optimal configuration settings and below PLL
warning during bootup was reported during video iris testing. 

[    3.327753] Lucid PLL latch failed. Output may be unstable!

The multi PD support helps to fix the above warning.  


>> So I think there's a mistake in understanding the backwards compatibility
>> paradigm here.
>>
>> There exists a single, objectively correct and represented in hardware,
>> list of required power-domains and the commit that caused the schema
>> validation errors was essentially "align YAML with reality" which should
>> be coupled with an immediate DT update to match and we forget about the
>> incomplete past
> 
> I'd second that. Let's make sure that the _driver_ works with old DT.
> But we don't have to support old DT in schema.
> 

Yes, The driver code is already backward compatible with the older DT.

Thanks,
Jagadeesh