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

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Message-ID: <94b75177-9401-4e0c-966b-5847a29cb6f7@linaro.org>
Date: Tue, 15 Jul 2025 12:20:01 +0300
From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Bryan O'Donoghue <bryan.odonoghue@...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: Bryan O'Donoghue <bod@...nel.org>, 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 7/15/25 12:01, Konrad Dybcio wrote:
> On 7/15/25 8:35 AM, Vladimir Zapolskiy wrote:
>> On 7/15/25 03:13, Bryan O'Donoghue wrote:
>>> On 14/07/2025 16:30, Vladimir Zapolskiy wrote:
>>>>>
>>>>> I think that is genuinely something we should handle in camss-csid.c
>>>>> maybe with some meta-data inside of the ports/endpoints..
>>>>>
>>>>
>>>> This is a CSIPHY property, a CSIPHY hardware configuration and a wiring
>>>> of sensors to a CSIPHY. Where is the relation to CSID here? There is no.
>>>
>>> All the PHY really needs to know is the # of lanes in aggregate, which
>>> physical lanes to map to which logical lanes and the pixel clock.
>>>
>>> We should add additional support to the Kernel's D-PHY API parameters
>>> mechanism to support that physical-to-logical mapping but, that's not
>>> required for this series or for any currently know upstream user of CAMSS.
>>>
>>>> Please share at least a device tree node description, which supports
>>>> a connection of two sensors to a single CSIPHY, like it shall be done
>>>> expectedly.
>>> &camss {
>>>        port@0 {
>>>            csiphy0_lanes01_ep: endpoint0 {
>>>                data-lanes = <0 1>;
>>>                remote-endpoint = <&sensor0_ep>;
>>>            };
>>>
>>>            csiphy0_lanes23_ep: endpoint0 {
>>>                data-lanes = <2 3>;
>>>                remote-endpoint = <&sensor1_ep>;
>>>            };
>>>         };
>>> };
>>
>> Don't you understand that this is broken?.. That's no good.
>>
>> Please listen and reread the messages given to you above, your proposed
>> "solution" does not support by design a valid hardware setup of two
>> sensors connected to the same CSIPHY.
>>
>> I would propose to stop force pushing an uncorrectable dt scheme, it
>> makes no sense.
> 
> If all you're asking for is an ability to grab an of_graph reference
> from the camss (v4l2) driver, you can simply do something along the
> lines of of_graph_get_remote_port(phy->dev->of_node)
> 

It's not about the driver specifics, my comment is about a proper
hardware description in dts notation, please see the device tree node
names.

-- 
Best wishes,
Vladimir