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Message-ID: <e57382ab-44fa-c141-98f6-8047aa96a6fb@pengutronix.de>
Date:   Tue, 8 Mar 2022 10:53:20 +0100
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Subject: Re: [PATCH v8 1/2] dt-bindings: arm: Add OP-TEE transport for SCMI
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To:     Etienne Carriere <etienne.carriere@linaro.org>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Sudeep Holla <sudeep.holla@arm.com>,
        Cristian Marussi <cristian.marussi@arm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Pengutronix Kernel Team <kernel@pengutronix.de>
References: <20211028140009.23331-1-etienne.carriere@linaro.org>
 <58a0e791-9573-99c2-0cc5-3920a1048113@pengutronix.de>
 <CAN5uoS_DQNkG8J0C-oT8aC-Xfozy9hgwAge_x2e4S-HOhSn5=w@mail.gmail.com>
 <CAN5uoS8QotrsoWYX3rCjxCKQFJNhFBXHc6JDYAn1rcX6N5mj4w@mail.gmail.com>
From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
In-Reply-To: <CAN5uoS8QotrsoWYX3rCjxCKQFJNhFBXHc6JDYAn1rcX6N5mj4w@mail.gmail.com>
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Hell Etienne,

On 01.03.22 15:11, Etienne Carriere wrote:
> Hi sorry,
> 
> I sent the mail while i was still typing it...
> Here is with the full answer.

Thanks for taking the time.

> On Tue, 1 Mar 2022 at 15:05, Etienne Carriere
> <etienne.carriere@linaro.org> wrote:
>>
>> Hello Ahmad,
>>
>> On Mon, 28 Feb 2022 at 17:01, Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>>>
>>> Hello Etienne,
>>>
>>> On 28.10.21 16:00, Etienne Carriere wrote:
>>>> Introduce compatible "linaro,scmi-optee" for SCMI transport channel
>>>> based on an OP-TEE service invocation. The compatible mandates a
>>>> channel ID defined with property "linaro,optee-channel-id".
>>>
>>> I just found this thread via the compatible in the STM32MP131 patch set:
>>> https://lore.kernel.org/all/20220225133137.813919-1-gabriel.fernandez@foss.st.com/
>>>
>>> Linux doesn't care whether PSCI is provided by TF-A, OP-TEE or something
>>> else, so there is just the arm,psci* compatible.
>>>
>>> What's different about SCMI that this is not possible? Why couldn't the
>>> existing binding and driver be used to communicate with OP-TEE as secure
>>> monitor as well?
>>
>> Compatible "linaro,scmi-optee" denote a alternate SCMI transport to
>> those already in v5.16.
> 
> It is names scmi-optee because the interface exposed to access SCMI services is
> based on TEE's interface (UUID to open a session with and invoke commands).

I gathered as much, but I didn't understand why it had to be an extra transport
when SCMI over SMC already exists. Sudeep cleared this point up for me.

Cheers,
Ahmad

> 
> The compatible is described in the Linux Documentation but not yet
> merged in the linux-next.
> It can be found in the tree of arm_scmi driver maintainers:
> https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git/log/?h=for-linux-next
> 
> This commit:
> https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git/commit/?h=for-linux-next&id=b7d2cf7c817b86e705b97f72c6be192a6760a14f
> 
> Br,
> Etienne
> 
>>
>>
>>>
>>> Cheers,
>>> Ahmad
>>>
>>>>
>>>> Cc: devicetree@vger.kernel.org
>>>> Cc: Rob Herring <robh+dt@kernel.org>
>>>> Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
>>>> ---
>>>> Changes since v6:
>>>>  - Remove maxItems from linaro,optee-channel-id description
>>>>
>>>> No change since v5
>>>>
>>>> Changes since v4:
>>>>  - Fix sram node name in DTS example: s/-shm-/-sram-/
>>>>
>>>> Changes since v3:
>>>>  - Add description for linaro,optee-channel-id in patternProperties
>>>>    specifying protocol can optionaly define a dedicated channel id.
>>>>  - Fix DTS example (duplicated phandles issue, subnodes ordering)
>>>>  - Fix typo in DTS example and description comments.
>>>>
>>>> Changes since v2:
>>>>  - Define mandatory property linaro,optee-channel-id
>>>>  - Rebased on yaml description file
>>>>
>>>> Changes since v1:
>>>>  - Removed modification regarding mboxes property description.
>>>> ---
>>>>  .../bindings/firmware/arm,scmi.yaml           | 65 +++++++++++++++++++
>>>>  1 file changed, 65 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
>>>> index 5c4c6782e052..eae15df36eef 100644
>>>> --- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
>>>> +++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
>>>> @@ -38,6 +38,9 @@ properties:
>>>>                       The virtio transport only supports a single device.
>>>>          items:
>>>>            - const: arm,scmi-virtio
>>>> +      - description: SCMI compliant firmware with OP-TEE transport
>>>> +        items:
>>>> +          - const: linaro,scmi-optee
>>>>
>>>>    interrupts:
>>>>      description:
>>>> @@ -83,6 +86,11 @@ properties:
>>>>      description:
>>>>        SMC id required when using smc or hvc transports
>>>>
>>>> +  linaro,optee-channel-id:
>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>> +    description:
>>>> +      Channel specifier required when using OP-TEE transport.
>>>> +
>>>>    protocol@11:
>>>>      type: object
>>>>      properties:
>>>> @@ -195,6 +203,12 @@ patternProperties:
>>>>          minItems: 1
>>>>          maxItems: 2
>>>>
>>>> +      linaro,optee-channel-id:
>>>> +        $ref: /schemas/types.yaml#/definitions/uint32
>>>> +        description:
>>>> +          Channel specifier required when using OP-TEE transport and
>>>> +          protocol has a dedicated communication channel.
>>>> +
>>>>      required:
>>>>        - reg
>>>>
>>>> @@ -226,6 +240,16 @@ else:
>>>>        - arm,smc-id
>>>>        - shmem
>>>>
>>>> +  else:
>>>> +    if:
>>>> +      properties:
>>>> +        compatible:
>>>> +          contains:
>>>> +            const: linaro,scmi-optee
>>>> +    then:
>>>> +      required:
>>>> +        - linaro,optee-channel-id
>>>> +
>>>>  examples:
>>>>    - |
>>>>      firmware {
>>>> @@ -340,7 +364,48 @@ examples:
>>>>                  reg = <0x11>;
>>>>                  #power-domain-cells = <1>;
>>>>              };
>>>> +        };
>>>> +    };
>>>> +
>>>> +  - |
>>>> +    firmware {
>>>> +        scmi {
>>>> +            compatible = "linaro,scmi-optee";
>>>> +            linaro,optee-channel-id = <0>;
>>>> +
>>>> +            #address-cells = <1>;
>>>> +            #size-cells = <0>;
>>>> +
>>>> +            scmi_dvfs1: protocol@13 {
>>>> +                reg = <0x13>;
>>>> +                linaro,optee-channel-id = <1>;
>>>> +                shmem = <&cpu_optee_lpri0>;
>>>> +                #clock-cells = <1>;
>>>> +            };
>>>> +
>>>> +            scmi_clk0: protocol@14 {
>>>> +                reg = <0x14>;
>>>> +                #clock-cells = <1>;
>>>> +            };
>>>> +        };
>>>> +    };
>>>>
>>>> +    soc {
>>>> +        #address-cells = <2>;
>>>> +        #size-cells = <2>;
>>>> +
>>>> +        sram@51000000 {
>>>> +            compatible = "mmio-sram";
>>>> +            reg = <0x0 0x51000000 0x0 0x10000>;
>>>> +
>>>> +            #address-cells = <1>;
>>>> +            #size-cells = <1>;
>>>> +            ranges = <0 0x0 0x51000000 0x10000>;
>>>> +
>>>> +            cpu_optee_lpri0: optee-sram-section@0 {
>>>> +                compatible = "arm,scmi-shmem";
>>>> +                reg = <0x0 0x80>;
>>>> +            };
>>>>          };
>>>>      };
>>>>
>>>
>>>
>>> --
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> 


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