linux-kernel - Re: [PATCH 05/11] dt-bindings: document the Qualcomm TEE Shared Memory Bridge

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Message-ID: <48feda07-525d-4319-ba09-14928ab1fd29@linaro.org>
Date:   Tue, 29 Aug 2023 11:30:06 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Alex Elder <elder@...aro.org>,
        Srini Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     kernel@...cinc.com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 05/11] dt-bindings: document the Qualcomm TEE Shared
 Memory Bridge

On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
>> mechanism that allows sharing memory buffers between trustzone and the
>> kernel.
> 
> Subject prefix:
> dt-bindings: firmware:
> 
> 
> 
>>
>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>> ---
>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
>>  1 file changed, 36 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>> new file mode 100644
>> index 000000000000..f660962b7b86
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>> @@ -0,0 +1,36 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: QCOM Shared Memory Bridge
>> +
>> +description: |
> 
> Do not need '|' unless you need to preserve formatting.
> 
>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
>> +
>> +maintainers:
>> +  - Bjorn Andersson <andersson@...nel.org>
>> +  - Konrad Dybcio <konrad.dybcio@...aro.org>
>> +  - Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>> +
>> +properties:
>> +  compatible:
>> +    items:
>> +      - enum:
>> +          - qcom,shm-bridge-sa8775p
>> +          - qcom,shm-bridge-sm8150
>> +          - qcom,shm-bridge-sm8450
>> +      - const: qcom,shm-bridge
>> +
> 
> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
> you need new binding if you do not have any resources here and the block
> is essentially feature of qcom,scm firmware?
Since it's "discoverable" (via retval of an scm call), I'd second the
idea of probing this from within the SCM driver.

Konrad