linux-kernel - Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video node

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Message-ID: <85f62a4b-cec8-48a1-a232-7f904371e390@quicinc.com>
Date: Sat, 5 Jul 2025 00:45:10 +0530
From: Vikash Garodia <quic_vgarodia@...cinc.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Dmitry Baryshkov
	<dmitry.baryshkov@....qualcomm.com>
CC: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Krzysztof Kozlowski
	<krzk@...nel.org>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        "Abhinav
 Kumar" <abhinav.kumar@...ux.dev>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, <linux-media@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video
 node


On 7/4/2025 1:53 PM, Bryan O'Donoghue wrote:
> On 03/07/2025 22:23, Dmitry Baryshkov wrote:
>>> I still give my RB for the series.
>>>
>>> To me the only question is should it be applied to sm8550 or to new SoCs
>>> from now on, sa8775p, x1e and derivatives.
>> I think we need to apply it to_all_ SoCs, maybe starting from MSM8x26
>> and MSM8x16. Likewise, we need to think bout secure buffers usecase. And
>> once we do that, we will realize that it also changes the ABI for all
>> SoCs that support either Venus or Iris.
> 
> I think a dts change is a non-starter as its an ABI break.
> 
> So if ABI break is out and reworking future dts to allow for a new device is
> out, then some API change is needed to allow the driver to stop the kernel
> automatically setting up the IOMMUs, create the new device as a platform device
> not dependent on DT change and have the probe() of the relevant drivers setup
> their own IOMMU extents based on - probably indexes we have in the driver
> configuration parameters.

The concept of sub device is nothing new, it has been there for firmware iommus
on venus bindings [1] and i am just extending it for non-pixel on iris. So
instead of complicating the driver, pls relook into the existing solution which
looks much simpler.

The proposal to dis-associate from DT would certainly bite us in future when we
have more and more iommu configurations, lets say "qcom,iommu-vmid" [2], comes
in for managing secure stream-ids.

[1]
https://elixir.bootlin.com/linux/v6.16-rc4/source/Documentation/devicetree/bindings/media/qcom,venus-common.yaml#L50

[2] https://lore.kernel.org/all/20231101071144.16309-2-quic_gkohli@quicinc.com/