Message-ID: <08c8cdfd-099e-7b90-b163-23ecee3a5da4@quicinc.com>
Date: Wed, 2 Jul 2025 17:02:50 +0530
From: Vikash Garodia <quic_vgarodia@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        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 7/2/2025 4:43 PM, Krzysztof Kozlowski wrote:
> 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.
I could not get this, are you suggesting to drop this reference ?
> 
>> 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?
Its not about hardware started to have a new stream-ID. You can look for the
description in the commit which explains the need for a new device and hence the
split of stream-IDs in iris device OR non-pixel device.
> 
>>  
>>    dma-coherent: true
>>  
>> +  non-pixel:
> 
> Why EXISTING hardware grows?
Same here, the commit describes the limitation of existing design and also
explains the need for having the non-pixel device. Its not that the hardware is
growing here, rather the hardware stream-IDs are utilized differently to get
higher device addressable range.
> 
>> +    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?
Again, explained the "excluded" portion from IOVA part in commit description.
For such excluded region, reserved memory would be needed. I have followed the
adsp example in the reserved-memory schema[1], its same for iris.

[1]
https://github.com/devicetree-org/dt-schema/blame/main/dtschema/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>;
> 
> Why do you need this?
Was planning to drop this, as the reserved-memory region have it defined.
> 
>> +
>> +      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.
Same query here, the commit well explains the limitation with existing device
and how adding a new sub node mitigates the situation.

Regards,
Vikash
> 
>>          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

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