linux-kernel - Re: [PATCH v3 1/5] media: dt-bindings: add non-pixel property in iris schema

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Message-ID: <19dd2e69-ad13-46f2-b99f-04a5e26f10d3@kernel.org>
Date: Wed, 2 Jul 2025 13:13:33 +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 v3 1/5] media: dt-bindings: add non-pixel property in iris
 schema

On 27/06/2025 17:48, 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 reference to the reserve-memory schema, which defines reserved IOVA

No. That schema is always selected. This makes no sense at all.

> regions that are *excluded* from addressable range. Video hardware
> generates different stream IDs based on the predefined 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.
> Non-pixel stream-ID can now be part of the new sub-node, hence iommus in
> iris node can have either 1 entry for pixel stream-id or 2 entries for
> pixel and non-pixel stream-ids.
> 
> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
> ---
>  .../bindings/media/qcom,sm8550-iris.yaml           | 40 ++++++++++++++++++++--
>  1 file changed, 38 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> index c79bf2101812d83b99704f38b7348a9f728dff44..4dda2c9ca1293baa7aee3b9ee10aff38d280fe05 100644
> --- a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> +++ b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> @@ -65,10 +65,31 @@ properties:
>        - const: core
>  
>    iommus:
> +    minItems: 1
>      maxItems: 2

No, why hardware suddenly has different amount?

>  
>    dma-coherent: true
>  
> +  non-pixel:

Why EXISTING hardware grows?

> +    type: object
> +    additionalProperties: false
> +
> +    description:
> +      Non pixel context bank is needed when video hardware have distinct iommus
> +      for non pixel buffers. Non pixel buffers are mainly compressed and
> +      internal buffers.
> +
> +    properties:
> +      iommus:
> +        maxItems: 1
> +
> +      memory-region:
> +        maxItems: 1
> +
> +    required:
> +      - iommus
> +      - memory-region
> +
>    operating-points-v2: true
>  
>    opp-table:
> @@ -86,6 +107,7 @@ required:
>  
>  allOf:
>    - $ref: qcom,venus-common.yaml#
> +  - $ref: /schemas/reserved-memory/reserved-memory.yaml

This makes no sense. how is this device a reserved memory?

>    - if:
>        properties:
>          compatible:
> @@ -117,6 +139,16 @@ examples:
>      #include <dt-bindings/power/qcom-rpmpd.h>
>      #include <dt-bindings/power/qcom,rpmhpd.h>
>  
> +    reserved-memory {
> +      #address-cells = <2>;
> +      #size-cells = <2>;

Why do you need this?

> +
> +      iris_resv: reservation-iris {

Mixing MMIO and non-MMIO is not the way to go. This is also not relevant
here. Don't embed other things into your binding example.


> +        iommu-addresses = <&iris_non_pixel 0x0 0x0 0x0 0x25800000>,
> +                          <&iris_non_pixel 0x0 0xe0000000 0x0 0x20000000>;
> +      };
> +    };
> +
>      video-codec@...0000 {
>          compatible = "qcom,sm8550-iris";
>          reg = <0x0aa00000 0xf0000>;
> @@ -144,12 +176,16 @@ examples:
>          resets = <&gcc GCC_VIDEO_AXI0_CLK_ARES>;
>          reset-names = "bus";
>  
> -        iommus = <&apps_smmu 0x1940 0x0000>,
> -                 <&apps_smmu 0x1947 0x0000>;
> +        iommus = <&apps_smmu 0x1947 0x0000>;

Why did the device or hardware change? Nothing explains in commit msg
what is wrong with existing device and existing binding.

>          dma-coherent;
>  
>          operating-points-v2 = <&iris_opp_table>;
>  
> +        iris_non_pixel: non-pixel {
> +            iommus = <&apps_smmu 0x1940 0x0000>;
> +            memory-region = <&iris_resv>;
> +        };
> +
>          iris_opp_table: opp-table {
>              compatible = "operating-points-v2";
>  
> 


Best regards,
Krzysztof