linux-kernel - Re: [PATCH 1/5] dt-bindings: media: qcom,sm8550-iris: add non_pixel and resv

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Message-ID: <4c6233d9-be7b-baf3-fb05-3ea007e35330@quicinc.com>
Date: Mon, 23 Jun 2025 15:31:19 +0530
From: Vikash Garodia <quic_vgarodia@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Dikshita Agarwal
	<quic_dikshita@...cinc.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        "Bryan
 O'Donoghue" <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
CC: <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] dt-bindings: media: qcom,sm8550-iris: add non_pixel
 and resv_region properties


On 6/20/2025 12:09 PM, Krzysztof Kozlowski wrote:
> On 20/06/2025 08:20, Vikash Garodia wrote:
>> Existing definition limits the IOVA to an addressable range of 4GiB, and
>> even within that range, some of the space is used by IO registers,
>> thereby limiting the available IOVA to even lesser. Video hardware is
>> designed to emit different stream-ID for pixel and non_pixel buffers,
>> thereby introduce a non_pixel sub node to handle non_pixel stream-ID.
>>
>> With this, both iris and non_pixel device can have IOVA range of 0-4GiB
>> individually. Certain video usecases like higher video concurrency needs
>> IOVA higher than 4GiB.
>>
>> Add the "resv_region" property, which defines reserved IOVA regions that
>> are *excluded* from addressable range. Video hardware generates
>> different stream IDs based on the range of IOVA addresses. Thereby IOVA
>> addresses for firmware and data buffers need to be non overlapping. For
>> ex. 0x0-0x25800000 address range is reserved for firmware stream-ID,
>> while non_pixel (bitstream ) stream-ID can be generated by hardware only
>> when bitstream buffers IOVA address is from 0x25800000-0xe0000000.
>>
>> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
>> ---
>>  .../bindings/media/qcom,sm8550-iris.yaml           | 35 ++++++++++++++++++++++
>>  1 file changed, 35 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
>> index c79bf2101812d83b99704f38b7348a9f728dff44..a1e83bae3c36f3a4c58b212ef457905e38091b97 100644
>> --- a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
>> +++ b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
>> @@ -65,10 +65,45 @@ properties:
>>        - const: core
>>  
>>    iommus:
>> +    minItems: 1
> 
> As discussed in other patchset, this needs clear explanation, so
> imperfect patch won't be used in future discussions as argument to take
> more of such things.
ACK.
> 
>>      maxItems: 2
>>  
>>    dma-coherent: true
>>  
>> +  resv_region:
> 
> DTS coding style. Anyway, regions go with memory-region bindings. Use that.
Sorry for a basic query here - I was reading through memory-region bindings in
[1]. My requirement is exactly same as the schema defined in [2] ex. adsp_resv.
Would it be more appropriate to extend reserved-memory.yaml, something like
below in iris yaml
allOf:
  - $ref: reserved-memory.yaml

Or any other approach to reference to [2] in iris yaml ?

[1]https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/reserved-memory/memory-region.yaml

[2]https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/reserved-memory/reserved-memory.yaml

Regards,
Vikash
> 
> Best regards,
> Krzysztof