linux-kernel - Re: [PATCH v3 1/6] dt-bindings: crypto: Document support for SPAcc

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Message-ID: <cd6e92af-1304-4078-9ed7-de1cb53c66da@kernel.org>
Date: Wed, 4 Jun 2025 16:07:43 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Pavitrakumar Managutte <pavitrakumarm@...avyalabs.com>
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, herbert@...dor.apana.org.au, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, Ruud.Derwig@...opsys.com,
 manjunath.hadli@...avyalabs.com, adityak@...avyalabs.com,
 Bhoomika Kadabi <bhoomikak@...avyalabs.com>
Subject: Re: [PATCH v3 1/6] dt-bindings: crypto: Document support for SPAcc

On 04/06/2025 14:20, Pavitrakumar Managutte wrote:
>>
>>>>> +
>>>>> +  snps,vspacc-id:
>>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>>> +    description: |
>>>>> +      Virtual SPAcc instance identifier.
>>>>> +      The SPAcc hardware supports multiple virtual instances (determined by
>>>>> +      ELP_SPACC_CONFIG_VSPACC_CNT parameter), and this ID is used to identify
>>>>> +      which virtual instance this node represents.
>>>>
>>>> No, IDs are not accepted.
>>>
>>> PK: This represents the specific virtual SPAcc that is being used in
>>> the current configuration. It is used to index into the register banks
>>> and the context memories of the virtual SPAcc that is being used. The
>>> SPAcc IP can be configured as dedicated virtual SPAccs in
>>> heterogeneous environments.
>>
>> OK. Why registers are not narrowed to only this instance? It feels like
>> you provide here full register space for multiple devices and then
>> select the bank with above ID.
> 
> PK: No, we cant narrow the registers to only this instance since its
> is just a single SPAcc with multiple virtual SPAcc instances. The same
> set of registers(aka register banks) and context memories are
> repeated, but sit at different offset addresses (i*4000 +
> register-offsets). The crypto hardware engine inside is shared by all
> the virtual SPAccs. This is very much for a heterogeneous computing
> scenario.

Then maybe you have one crypto engine? You ask us to guess all of this,
also because you do not upstream the DTS for real product. Any
mentioning of "virtual" already raises concerns...

Best regards,
Krzysztof