linux-kernel - Re: [PATCH v7 00/15] Add dt-bindings and dtsi changes for CAMSS on x1e80100 silicon

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Message-ID: <ae0a309f-7e52-4d3c-8f26-989f22da5b07@linaro.org>
Date: Tue, 15 Jul 2025 09:48:51 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Vladimir Zapolskiy <vladimir.zapolskiy@...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>, Robert Foss <rfoss@...nel.org>,
 Todor Tomov <todor.too@...il.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v7 00/15] Add dt-bindings and dtsi changes for CAMSS on
 x1e80100 silicon

On 15/07/2025 07:53, Vladimir Zapolskiy wrote:
>>    Finally I believe we should contine to have endpoints go from the 
>> sensor
>>    to CAMSS not the PHY as CAMSS' CSI decoder is the consumer of the data
>>    not the PHY.
>>
> 
> 1. This is an incorrect assumption, unfortunately it was not discussed
> previously for whatever reason, good news now it gets a discussion under
> drivers/phy changeset.

Perhaps you can explain why ?

Taking the example of other setups similar to CAMSS I believe as laid 
out above we should have

- Dedicated CSIPHY nodes
- Use the upstream PHY API

I believe individual CSIPHY nodes and endpoints from sensor to CSID are 
more consistent with established upstream schema.

> 2. The whole new changes for legacy/new CSIPHY support is not present
> in v1-v6 of this changeset, it just appears out of nowhere in the v7,
> and since it is broken it should be removed from v8 expectedly.
Broken how though ?

> It's a pity to realize that instead of providing any review comments
> for the CSIPHY support series sent to you one month ago a lot of time
> is wastefully burnt on a broken by design change development.

I've been working on this on-and-off since the end of April:
Link: 
https://lore.kernel.org/linux-media/c5cf0155-f839-4db9-b865-d39b56bb1e0a@linaro.org

The length of time isn't a good argument to apply a patch but, of course 
its annoying.

The rationale here is:

- Follow existing examples and best practices [1][2][3]
- Minimize code bombs being generally conservative
   in the amount of churn going in per release cycle
- Help people get changes merged - which can conflict with the
   previous statement

Which from my reading of the state of the art means:

- Dedicated CSIPHY nodes
- Endpoints from sensor to CSI decoder
- And picking up on point #2 above minimizing the churn

[1] Documentation/devicetree/bindings/phy/rockchip-inno-csi-dphy.yaml
[2] Documentation/devicetree/bindings/phy/mediatek,mt8365-csi-rx.yaml
[3] 
https://lore.kernel.org/linux-media/20240220-rk3568-vicap-v9-12-ace1e5cc4a82@collabora.com/

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bod