linux-kernel - Re: [PATCH v2 2/6] dt-bindings: media: camss: Add qcom,kaanapali-camss binding

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Message-ID: <a0d9389b-67a5-458a-858b-ffdd95f7ccc6@linaro.org>
Date: Thu, 16 Oct 2025 02:32:15 +0300
From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Hangxiang Ma <hangxiang.ma@....qualcomm.com>,
 Loic Poulain <loic.poulain@....qualcomm.com>, Robert Foss
 <rfoss@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Todor Tomov <todor.too@...il.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-i2c@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, aiqun.yu@....qualcomm.com,
 tingwei.zhang@....qualcomm.com, trilok.soni@....qualcomm.com,
 yijie.yang@....qualcomm.com, Jingyi Wang <jingyi.wang@....qualcomm.com>,
 Atiya Kailany <atiya.kailany@....qualcomm.com>
Subject: Re: [PATCH v2 2/6] dt-bindings: media: camss: Add
 qcom,kaanapali-camss binding

On 10/16/25 00:43, Bryan O'Donoghue wrote:
> On 15/10/2025 20:45, Vladimir Zapolskiy wrote:
>>> +  power-domains:
>>> +    items:
>>> +      - description:
>>> +          TFE0 GDSC - Thin Front End, Global Distributed Switch
>>> Controller.
>>> +      - description:
>>> +          TFE1 GDSC - Thin Front End, Global Distributed Switch
>>> Controller.
>>> +      - description:
>>> +          TFE2 GDSC - Thin Front End, Global Distributed Switch
>>> Controller.
>>> +      - description:
>>> +          Titan GDSC - Titan ISP Block Global Distributed Switch
>>> Controller.
>>> +
>>> +  power-domain-names:
>>> +    items:
>>> +      - const: tfe0
>>> +      - const: tfe1
>>> +      - const: tfe2
>>
>> Please remove all 'tfeX' power domains, they are not going to be utilized
>> any time soon.
>>
>> When 'power-domains' list is just a single Titan GDSC, 'power-domain-names'
>> property is not needed.
> 
> Each one of these TFEs powers an individually power-collapsible TFEs.
> 
> This is also so with the other xFE power-domains on previous SoC
> generations.

This is false, for instance there is no management of SFEx power domains
in SM8550 or X1E80100 CAMSS in the upstrem, neither there is no management
of SBI, IPE, BPS, CPP and so on GDSC power domans given by CAMCCs.

TFEx is no more special, if it's unused, then it should not be added.

> 
> You'll need the TFEx power-domain to process any data on TFEx with the
> 'lite' versions being tied to the TOP GDSC.

When it is needed, the documentation will be updated accordingly, right now
it is unknown what a data processing on TFEx looks like, it might happen
that there will be separate device tree nodes for TFEx.

TFEx power domains shall be removed right now, unti; a usecase in the upstream
CAMSS appears to use them, I haven't seen such code at the moment.

-- 
Best wishes,
Vladimir