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

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Message-ID: <2bd17ab5-950c-4260-ae7c-9ba9a6441496@oss.qualcomm.com>
Date: Fri, 20 Jun 2025 19:27:03 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        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 6/20/25 8:39 AM, 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.
> 
>>      maxItems: 2
>>  
>>    dma-coherent: true
>>  
>> +  resv_region:
> 
> DTS coding style. Anyway, regions go with memory-region bindings. Use that.

On a tangent, FWIW this is a discussion related to this patchset that
never got much attention:

https://lore.kernel.org/linux-devicetree/9439182e-3338-4d57-aa02-b621bc9498a3@oss.qualcomm.com/

Konrad