linux-kernel - Re: [PATCH 2/2] phy: qcom-mipi-csi2: Add a CSI2 MIPI D-PHY driver

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Message-ID: <84eea632-02d8-4b7f-a4ca-36ce7159a170@linaro.org>
Date: Tue, 22 Jul 2025 11:59:59 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
 Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
 linux-media@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] phy: qcom-mipi-csi2: Add a CSI2 MIPI D-PHY driver

On 22/07/2025 11:08, Bryan O'Donoghue wrote:
> On 22/07/2025 09:32, Neil Armstrong wrote:
>> The whole key point here is the combo mode, as I understood the combo mode feature
>> makes the PHY lanes available as 2 separate streams, like if you got 2 "controllers"
>> attached to the same PHY. So in fact, the PHY should have a single node, but 2 PHY
>> interfaces in combo mode.
>>
>> This makes all this controller/phy model very complex to handle and add a lot of
>> logic in the camss side. Moving the "csiphy" as an independent media device that
>> can declare up to 2 endpoints in combo mode makes things much simpler, and allows
>> us to attach each "csiphy" stream to any "controller" side of camss.
> 
> I think there should be a generic extension to PHY/linux-media to support that instead of something Qualcomm specific.

Can you point out what's missing ? AFAIK it's more a matter of proper representation of all
the CAMSS components with a proper ports/endpoint graph design that adding new kernel APIs.

Neil

> 
> The first task is qcom/CAMSS specific which is separate the CSIPHYs out from the CAMSS block - done in this series and do so in a way that doesn't break the existing ABI - done in the context of adding Hamoa/x1e.
> 
> The second step should be to extend the existing linux-media and PHY API to support multiple sensors on the same CSIPHY in a generic way.
> 
> If you want to ship me some hardware, I'll help.
> 
> ---
> bod