linux-kernel - Re: [PATCH v2 2/4] dt-bindings: remoteproc: Add compatibility for TEE support

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Message-ID: <75429209-8f30-4880-8f92-ecb3cf90ae33@linaro.org>
Date: Fri, 26 Jan 2024 12:03:25 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Mathieu Poirier <mathieu.poirier@...aro.org>,
 Jens Wiklander <jens.wiklander@...aro.org>, Rob Herring
 <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-remoteproc@...r.kernel.org,
 linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/4] dt-bindings: remoteproc: Add compatibility for TEE
 support

On 18/01/2024 11:04, Arnaud Pouliquen wrote:
> The "st,stm32mp1-m4-tee" compatible is utilized in a system configuration
> where the Cortex-M4 firmware is loaded by the Trusted execution Environment
> (TEE).
> For instance, this compatible is used in both the Linux and OP-TEE
> device-tree:
> - In OP-TEE, a node is defined in the device tree with the
>   st,stm32mp1-m4-tee to support signed remoteproc firmware.
>   Based on DT properties, OP-TEE authenticates, loads, starts, and stops
>   the firmware.
> - On Linux, when the compatibility is set, the Cortex-M resets should not
>   be declared in the device tree.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
> V1 to V2 updates
> - update "st,stm32mp1-m4" compatible description to generalize
> - remove the 'reset-names' requirement in one conditional branch, as the
>   property is already part of the condition test.
> ---
>  .../bindings/remoteproc/st,stm32-rproc.yaml   | 52 +++++++++++++++----
>  1 file changed, 43 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml b/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml
> index 370af61d8f28..6af821b15736 100644
> --- a/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml
> +++ b/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml
> @@ -16,7 +16,12 @@ maintainers:
>  
>  properties:
>    compatible:
> -    const: st,stm32mp1-m4
> +    enum:
> +      - st,stm32mp1-m4
> +      - st,stm32mp1-m4-tee

The patch looks good to me, but I wonder about this choice of two
compatibles.

Basically this is the same hardware with the same interface, but two
compatibles to differentiate a bit different firmware setup. We have
already such cases for Qualcomm [1] [2] and new ones will be coming. [3]

I wonder whether this should be rather the same compatible with
additional property, e.g. "st,tee-control" or "remote-control".

[1]
https://elixir.bootlin.com/linux/v6.7.1/source/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml#L54

[2]
https://elixir.bootlin.com/linux/v6.7.1/source/Documentation/devicetree/bindings/net/qcom,ipa.yaml#L129
(that's a bit different)

[3] https://lore.kernel.org/linux-devicetree/20240124103623.GJ4906@thinkpad/

@Rob,
Any general guidance for this and Qualcomm?

Best regards,
Krzysztof