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Message-ID: <1b117e49-28d0-da75-68ee-c2fcef9fc9a9@linaro.org>
Date:   Tue, 24 May 2022 11:19:12 +0200
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Subject: Re: [PATCH v5 1/6] dt-bindings: remoteproc: Add Xilinx RPU subsystem
 bindings
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To:     Tanmay Shah <tanmay.shah@xilinx.com>, bjorn.andersson@linaro.org,
        mathieu.poirier@linaro.org, robh+dt@kernel.org, krzk+dt@kernel.org,
        michal.simek@xilinx.com
Cc:     linux-remoteproc@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
References: <20220518194426.3784095-1-tanmay.shah@xilinx.com>
 <20220518194426.3784095-2-tanmay.shah@xilinx.com>
 <45fea4a1-387f-9684-a90b-58b695b54172@linaro.org>
 <c97d61b0-8a38-5054-d5f1-bc7c5e7bcf61@xilinx.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <c97d61b0-8a38-5054-d5f1-bc7c5e7bcf61@xilinx.com>
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On 23/05/2022 23:38, Tanmay Shah wrote:
> 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?

Yes, although shrinking might not be allowed once binding is being used.

> 
> 
>>
>>> +        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.

That sounds fine.

> 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.

I see. If schema accepts such combination (listing items + maxItems +
additionalItems), then it's fine.

> 

Best regards,
Krzysztof