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Date:   Mon, 23 May 2022 14:38:52 -0700
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Subject: Re: [PATCH v5 1/6] dt-bindings: remoteproc: Add Xilinx RPU subsystem
 bindings
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To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        <bjorn.andersson@linaro.org>, <mathieu.poirier@linaro.org>,
        <robh+dt@kernel.org>, <krzk+dt@kernel.org>,
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References: <20220518194426.3784095-1-tanmay.shah@xilinx.com>
 <20220518194426.3784095-2-tanmay.shah@xilinx.com>
 <45fea4a1-387f-9684-a90b-58b695b54172@linaro.org>
From:   Tanmay Shah <tanmay.shah@xilinx.com>
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Thanks for reviews Krzysztof. Please find my comments below.

On 5/21/22 8:12 AM, Krzysztof Kozlowski wrote:
> On 18/05/2022 21:44, Tanmay Shah wrote:
>> +description: |
>> +  The Xilinx platforms include a pair of Cortex-R5F processors (RPU) for
>> +  real-time processing based on the Cortex-R5F processor core from ARM.
>> +  The Cortex-R5F processor implements the Arm v7-R architecture and includes a
>> +  floating-point unit that implements the Arm VFPv3 instruction set.
>> +
>> +properties:
>> +  compatible:
>> +    const: xlnx,zynqmp-r5fss
>> +
>> +  xlnx,cluster-mode:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    enum: [0, 1, 2]
>> +    description: |
>> +      The RPU MPCore can operate in split mode(Dual-processor performance), Safety
>> +      lock-step mode(Both RPU cores execute the same code in lock-step,
>> +      clock-for-clock) or Single CPU mode (RPU core 0 can be held in reset while
>> +      core 1 runs normally). The processor does not support dynamic configuration.
>> +      Switching between modes is only permitted immediately after a processor reset.
>> +      If set to  1 then lockstep mode and if 0 then split mode.
>> +      If set to  2 then single CPU mode. When not defined, default will be lockstep mode.
>> +
>> +patternProperties:
>> +  "^r5f-[a-f0-9]+$":
>> +    type: object
>> +    description: |
>> +      The RPU is located in the Low Power Domain of the Processor Subsystem.
>> +      Each processor includes separate L1 instruction and data caches and
>> +      tightly coupled memories (TCM). System memory is cacheable, but the TCM
>> +      memory space is non-cacheable.
>> +
>> +      Each RPU contains one 64KB memory and two 32KB memories that
>> +      are accessed via the TCM A and B port interfaces, for a total of 128KB
>> +      per processor. In lock-step mode, the processor has access to 256KB of
>> +      TCM memory.
>> +
>> +    properties:
>> +      compatible:
>> +        const: xlnx,zynqmp-r5f
>> +
>> +      power-domains:
>> +        description: RPU core PM domain specifier
>> +        maxItems: 1
>> +
>> +      mboxes:
>> +        items:
>> +          - description: mailbox channel to send data to RPU
>> +          - description: mailbox channel to receive data from RPU
>> +        minItems: 1
>> +
>> +      mbox-names:
>> +        items:
>> +          - const: tx
>> +          - const: rx
>> +        minItems: 1
>> +
>> +      sram:
>> +        $ref: /schemas/types.yaml#/definitions/phandle-array
>> +        minItems: 1
> maxItems instead


Here, I am not sure how many maxItems are really needed as TCM bindings 
are not
defined yet. For now, I will just keep maxItems as 8. i.e. 4 OCM banks 
and 4 TCM
banks. However, that can change once bindings are defined.
Is that fine?


>
>> +        description: |
>> +          phandles to one or more reserved on-chip SRAM regions. Other than TCM,
>> +          the RPU can execute instructions and access data from, the OCM memory,
>> +          the main DDR memory, and other system memories.
>> +
>> +          The regions should be defined as child nodes of the respective SRAM
>> +          node, and should be defined as per the generic bindings in,
>> +          Documentation/devicetree/bindings/sram/sram.yaml
>> +
>> +      memory-region:
>> +        description: |
>> +          List of phandles to the reserved memory regions associated with the
>> +          remoteproc device. This is variable and describes the memories shared with
>> +          the remote processor (e.g. remoteproc firmware and carveouts, rpmsg
>> +          vrings, ...). This reserved memory region will be allocated on DDR memory.
>> +        minItems: 1
>> +        items:
>> +          - description: region used for RPU firmware image section
>> +          - description: vdev buffer
>> +          - description: vring0
>> +          - description: vring1
>> +        additionalItems: true
> How did this one appear here? It does not look correct, so why do you
> need it?


Memory regions listed in items: field here are used for default current 
OpenAMP demos. However,
other demos can be developed by user that can use more number of memory 
regions.
As description says, memory-region can have variable number phandles 
based on
user requirement. So, by additionalItems I just want to notify that user can
define more number of regions. We can limit memory-regions with 
'maxItems: 8'.
In that case, I will add 'maxItems:' field in next revision and even, 
that can change in future.
But, User should have flexibility to define more memory regions than 
what is in list
of 'items:' field. I think this is similar to what is defined in 
ti,k3-r5 bindings.

Please let me know your thoughts.


>> +
>> +    required:
>> +      - compatible
>> +      - power-domains
>> +
>> +    unevaluatedProperties: false
>> +
>> +required:
>> +  - compatible
>> +\
> Best regards,
> Krzysztof