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

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Message-ID: <a35d3928-8ac6-49ab-8689-16ba69afe197@kernel.org>
Date: Fri, 20 Jun 2025 08:39:53 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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 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.

Best regards,
Krzysztof