linux-kernel - Re: [PATCH v7 1/7] media: dt-bindings: venus: Add qcm2290 dt schema

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Message-ID: <b72ae4cf-b107-4117-9289-61b0d550e49c@oss.qualcomm.com>
Date: Fri, 18 Jul 2025 12:21:03 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Jorge Ramirez <jorge.ramirez@....qualcomm.com>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>, quic_vgarodia@...cinc.com,
        quic_dikshita@...cinc.com, krzk+dt@...nel.org, konradybcio@...nel.org,
        mchehab@...nel.org, andersson@...nel.org, conor+dt@...nel.org,
        amit.kucheria@....qualcomm.com, linux-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/7] media: dt-bindings: venus: Add qcm2290 dt schema

On 7/18/25 12:04 PM, Krzysztof Kozlowski wrote:
> On 18/07/2025 12:02, Konrad Dybcio wrote:
>> On 7/18/25 8:27 AM, Krzysztof Kozlowski wrote:
>>> On 17/07/2025 19:00, Jorge Ramirez wrote:
>>>> On 17/07/25 13:16:31, Jorge Ramirez wrote:
>>>>> On 17/07/25 08:45:17, Krzysztof Kozlowski wrote:
>>>>>> On 17/07/2025 08:35, Jorge Ramirez wrote:
>>>>>>> On 17/07/25 00:22:53, Bryan O'Donoghue wrote:
>>>>>>>> On 15/07/2025 21:47, Jorge Ramirez-Ortiz wrote:
>>>>>>>>> Add a schema for the venus video encoder/decoder on the qcm2290.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez@....qualcomm.com>
>>>>>>>>> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>>>>>>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>>>>>>>>> ---
>>>>>>>>>   .../bindings/media/qcom,qcm2290-venus.yaml    | 127 ++++++++++++++++++
>>>>>>>>>   1 file changed, 127 insertions(+)
>>>>>>>>>   create mode 100644 Documentation/devicetree/bindings/media/qcom,qcm2290-venus.yaml
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/devicetree/bindings/media/qcom,qcm2290-venus.yaml b/Documentation/devicetree/bindings/media/qcom,qcm2290-venus.yaml
>>>>>>>>> new file mode 100644
>>>>>>>>> index 000000000000..0371f8dd91a3
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/Documentation/devicetree/bindings/media/qcom,qcm2290-venus.yaml
>>>>>>>>> @@ -0,0 +1,127 @@
>>>>>>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>>>>>>>> +%YAML 1.2
>>>>>>>>> +---
>>>>>>>>> +$id: http://devicetree.org/schemas/media/qcom,qcm2290-venus.yaml#
>>>>>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>>>>>> +
>>>>>>>>> +title: Qualcomm QCM2290 Venus video encode and decode accelerators
>>>>>>>>> +
>>>>>>>>> +maintainers:
>>>>>>>>> +  - Vikash Garodia <quic_vgarodia@...cinc.com>
>>>>>>>>
>>>>>>>> Shouldn't you be on this list ? If you upstream a file I think you should
>>>>>>>> list yourself as responsible for its glory or its mess.
>>>>>>>
>>>>>>> happy to do it. The MAINTAINER's file covered all the files named
>>>>>>
>>>>>> This should be the person(s) interested and caring about this hardware,
>>>>>> which means:
>>>>>> 1. Subsystem maintainers: no
>>>>>> 2. Driver maintainers: usually yes
>>>>>> 3. Author(s) of new hardware support: usually yes
>>>>>
>>>>> perfect, will do 
>>>>>
>>>>>>
>>>>>>> schemas/media/*venus* so my understanding was that I shouldn't.
>>>>>>
>>>>>> I cannot comment why people decided to go one way or another in other
>>>>>> code, but it as well could be just incorrect choice thinking only people
>>>>>> in MAINTAINERS care about hardware.
>>>>>>
>>>>>> ...
>>>>>>
>>>>>>>>> +
>>>>>>>>> +        memory-region = <&pil_video_mem>;
>>>>>>>>> +        iommus = <&apps_smmu 0x860 0x0>,
>>>>>>>>> +                 <&apps_smmu 0x880 0x0>,
>>>>>>>>> +                 <&apps_smmu 0x861 0x04>,
>>>>>>>>> +                 <&apps_smmu 0x863 0x0>,
>>>>>>>>> +                 <&apps_smmu 0x804 0xe0>;
>>>>>>>>
>>>>>>>> You're listing five iommus.
>>>>>>>>
>>>>>>>> I understand there's some disagreement about whether or not to list all of
>>>>>>>> the potential use-cases but, TBH I don't think those are good arguments.
>>>>>>>>
>>>>>>>> Unless there's some technical prohibition I can't think of listing all five
>>>>>>>> maxItems:5 .. let's just do that.
>>>>>>>
>>>>>>> since the device tree should describe hardware and not policy, and the
>>>>>>> driver seems to be able to ignore the unused SIDs I think this is the
>>>>>>> right thing to do.
>>>>>>
>>>>>>
>>>>>> It was never about the driver but about whether you should describe in
>>>>>> DTS for non-secure world the entries which are secure world. The answer
>>>>>> in general is that you can and there will be benefits (e.g. sharing DTS
>>>>>> with secure world implementations).
>>>>>
>>>>> all right, sounds good then, thanks
>>>>
>>>> Not sure if I’ve shared this before, but following an internal
>>>> discussion, I think it’s worth highlighting a functional dependency in
>>>> the current kernel:
>>>>
>>>>  - the driver only works if the first two IOMMUs in the list — the
>>>> non-secure ones — are placed at the beginning. Reordering them breaks
>>>> functionality, which introduces unexpected fragility.
>>>>
>>>> Regardless, this seems like a valid concern to me — a driver shouldn't
>>>> rely on the order of phandles — and I just wanted to make sure you're
>>>> aware of it before I post a v8 (likely sometime next week or the
>>>> following, as I’ll be taking a short break soon).
>>>
>>>
>>> Hm? Order of lists is strictly defined. That's actually an overlook that
>>> we never do it for iommus, but the core rule stays.
>>
>> (FWIW "items:" is an ordered list, "enum:" is unordered)
> 
> enum is not a list, but enumeration, meaning one item of multiple values.

Right, need more caffeine

Konrad