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

Vikash Garodia
2025-06-27T17:16:17Z

On 6/27/2025 10:01 PM, Bryan O'Donoghue wrote:
> On 27/06/2025 16:48, 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
>> 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@quicinc.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
>>       dma-coherent: true
>>   +  non-pixel:
>> +    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.
>
> You do a better job in the cover letter of describing what this is, why its
> needed etc.
>
> Not asking for this verbatim but its clearer:
>
> "All non pixel buffers, i.e bitstream, HFI queues
> and internal buffers related to bitstream processing, would be managed
> by this non_pixel device."
>
> Where does the term "non-pixel" come from if its a meaningful name wrt to the
> firmware then non-pixel is fine but, consider a name such as "out-of-band" or "oob"
It is in-sync with firmware and we would be seeing it more when we extend it for
secure usecases.

Regards,
Vikash
> out-of-band is a common term as is "sideband" but sideband I think has a
> different meaning, really this non-data/non-pixel data stuff is out-of-band.
>
> At least for the way the language pack I have installed in my brain right now,
> "oob" or "out-of-band" is a more intuitive name. Its really up to you though the
> main point would be to enumerate the description here with some of the detail
> you've put into the cover letter.
>
>> +
>> +    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
>>     - 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>;
>> +
>> +      iris_resv: reservation-iris {
>> +        iommu-addresses = <&iris_non_pixel 0x0 0x0 0x0 0x25800000>,
>> +                          <&iris_non_pixel 0x0 0xe0000000 0x0 0x20000000>;
>> +      };
>> +    };
>
> iris_oob would be less text in the end.
>
>> +
>>       video-codec@aa00000 {
>>           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>;
>>           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";
>>
>
> So I was trying to think of a way to catch you out with an ABI break but, I
> don't see how you add minItems: 1 to the iommus declaration above so dts prior
> to this change should still be valid.
>
> I think this adds up but, consider oob instead of non-pixel.
>
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
>
> ---
> bod