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

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Message-ID: <ea0d8afb-4d64-4fc5-996b-452420e750da@kernel.org>
Date: Tue, 24 Jun 2025 10:33:00 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 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 20/06/2025 19:27, Konrad Dybcio wrote:
> 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/


There is no patchset above, just email describing a problem. It did not
get attention maybe because of usual kernel process: show the code, we
do not have time to comment on every problem or idea.

Best regards,
Krzysztof