Message-ID: <63d9252c-77d5-4405-a395-d7664c35ea12@oss.qualcomm.com>
Date: Mon, 20 Oct 2025 10:42:09 -0700
From: Vijay Kumar Tumati <vijay.tumati@....qualcomm.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Loic Poulain <loic.poulain@....qualcomm.com>
Cc: Hangxiang Ma <hangxiang.ma@....qualcomm.com>,
        Jingyi Wang <jingyi.wang@....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>, Bryan O'Donoghue <bod@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>, 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
Subject: Re: [PATCH 2/6] dt-bindings: media: camss: Add qcom,kaanapali-camss
 binding


On 10/20/2025 3:56 AM, Bryan O'Donoghue wrote:
> On 20/10/2025 11:16, Krzysztof Kozlowski wrote:
>> On 16/10/2025 12:43, Krzysztof Kozlowski wrote:
>>> On 16/10/2025 10:47, Loic Poulain wrote:
>>>> On Thu, Oct 16, 2025 at 7:52 AM Krzysztof Kozlowski 
>>>> <krzk@...nel.org> wrote:
>>>>>
>>>>> On 15/10/2025 05:21, Hangxiang Ma wrote:
>>>>>>>> +      - const: csiphy4
>>>>>>>> +      - const: csiphy5
>>>>>>>> +      - const: vfe0
>>>>>>>> +      - const: vfe1
>>>>>>>> +      - const: vfe2
>>>>>>>> +      - const: vfe_lite0
>>>>>>>> +      - const: vfe_lite1
>>>>>>> Wouldn't it make sense to simplify this and have different camss 
>>>>>>> nodes
>>>>>>> for the 'main' and 'lite' paths?
>>>>>>>
>>>>>>> [...]
>>>>>> No such plan till now. Other series may take this into 
>>>>>> consideration.
>>>>>
>>>>> We don't care much about your plan. You are expected to send correct
>>>>> hardware description.
>>>>
>>>> To be fair, other platforms like sc8280xp-camss already have the
>>>> all-in big camss node.
>>>> Point is that if Lite and Main blocks are distinct enough we could
>>>> have two simpler nodes.
>>>> Would it make things any better from a dts and camss perspective?
>>>>
>>>>   camss: isp@...3000 {
>>>>      compatible = "qcom,kaanapali-camss";
>>>>      [...]
>>>> }
>>>>
>>>> camss-lite:ips@...3000 {
>>>>     compatible = "qcom,kaanapali-lite-camss";
>>>>      [...]
>>>> }
>>>>
>>>> That approach would create two distinct CAMSS instances and separate
>>>> media pipelines.
>>>> However, it may not work with the current implementation, as the CSI
>>>> PHYs would need to be shared between them.
>>>>
>>>> I guess this should be part of the broader discussion around
>>>> splitting/busifying CAMSS.
>>>
>>> And this discussion CAN happen now, stopping this camss and any future
>>> camss till we conclude the discussion. Whatever internal plans of that
>>> teams are, rejecting technical discussion based on "no plans for that"
>>> is a really bad argument, only stalling this patchset and raising 
>>> eyebrows.
>>
>>
>> To be clear, I expect Loic's comment to be fully and technically
>> addressed, not with "no plan for that".
>>
>> This blocks this patchset and any new versions.
>>
>> Best regards,
>> Krzysztof
>
> I think we should stick with the existing bindings.
>
> There is no "lite" ISP there are so-called lite blocks within the 
> CAMSS block.
>
> It makes sense to split out the PHYs from this block as they have 
> their own power-rails but, if you look at the block diagrams for this 
> IP there is no specific ISP lite, there are merely blocks within the 
> camera called lite.
>
> It might be nice to structure things like this 
> arch/arm64/boot/dts/rockchip/rk356x-base.dtsi with each component 
> separated out into its own node with its own compat string but, I'd 
> have a hard time justifying changing up the bindings we already have 
> for that reason - aside from anything else - all of those components 
> in CAMSS live inside of the TITAN_TOP_GDSC which is the power-domain 
> for the whole camera system.
>
> So not meaning to answer for Hangxiang but, I think the compelling 
> logic here is to stick to and extend the existing bindings.
>
> So in fact I have no problem with the bindings as submitted - not 
> including the regular fixups these types of submissions entail.
>
> ---
> bod
>
Hi @Bryan, @Krzysztof, just my two cents. I think we should consider 
separating CSIPHY, CSID, IFE and IFE Lite into distinct DT nodes. Having 
a modular DT structure brings in several advantages,

     1. Simple to manage with much better readability.
     2. Better control to disable certain HW modules from DT.
     3. Less error prone as we don't need to maintain long lists of 
clocks or other resources against their names. Accordingly, easy to review.
     4. No need to maintain resource lists within the CAMSS driver to 
identify the resources specific to the HW block. Offers centralized 
control for the HW resources.
     5. Allows re use between the platforms when a same version of a 
subset of HW modules is carried over to future chip sets.
     6. Is more scalable when we add more functionality to the CAMSS driver.
     7. Finally, it brings in parallel development ability with 
engineers (within the local teams) working on different HW modules 
within camera subsystem.

If not for the current patches in the pipeline, if you are comfortable 
with this approach, we will try to push the changes for the future chip 
sets with the modular bindings, leaving the existing SOC drivers and 
bindings untouched (if that's recommended). Please let us know your 
thoughts. Thanks.
>
>

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