linux-kernel - Re: [Linux-stm32] [PATCH v2 12/13] ARM: dts: stm32: enable optee firmware and SCMI support on STM32MP13

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Date:   Wed, 16 Mar 2022 12:01:10 +0100
From:   Etienne Carriere <etienne.carriere@...aro.org>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>,
        Gabriel FERNANDEZ <gabriel.fernandez@...s.st.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-stm32@...md-mailman.stormreply.com,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Etienne Carriere <etienne.carriere@...aro.org>
Subject: Re: [Linux-stm32] [PATCH v2 12/13] ARM: dts: stm32: enable optee
 firmware and SCMI support on STM32MP13

Hi Ahmad,

> Helo Gabriel,
>
> On 03.03.22 14:09, Gabriel FERNANDEZ wrote:
>>
>> On 2/25/22 16:13, Ahmad Fatoum wrote:
>>> Hello Gabriel,
>>>
>>> On 25.02.22 14:31, gabriel.fernandez@...s.st.com wrote:
>>>> From: Gabriel Fernandez <gabriel.fernandez@...s.st.com>
>>>> +    firmware {
>>>> +        optee {
>>>> +            method = "smc";
>>>> +            compatible = "linaro,optee-tz";
>>>> +        };
>>>> +
>>>> +        scmi: scmi {
>>>> +            compatible = "linaro,scmi-optee";
>>> This compatible doesn't seem to be documented upstream. I am looking at v5.17-rc5.
>>> Do you have a reference detailing the difference between this conduit and
>>> plain arm,scmi-smc (as used with TF-A on the STM32MP151).
>>>
>>> Cheers,
>>> Ahmad
>>
>> Hi
>>
>> Ahmad,
>>
>> it's on going.
>>
>> https://lore.kernel.org/linux-arm-kernel/20211029102118.GG6526@e120937-lin/T/#mf46c83f0aadce3061ee93fa22159405f38d881a0
>
> I've found that thread in the meantime and got some clarification on why a new
> transport for OP-TEE was added. One question I still have though is why make
> this transport the default for STM32MP13x instead of using SCMI over SMC like
> you do for STM32MP15x. OP-TEE could still be made to service SCMI over SMC
> and it would allow people employing TF-A as SCMI provider an easier migration
> to the newer SoC.
>

Just to rephrase a bit what's being said in the referred mail thread:
On STM32MP13x, there are SCMI messages that must be processed inside a
thread execution context in the SCMI server. There is no standard SMC
function ID defined that the SCMI/SMC transport could use for that
purpose. OP-TEE provides such a threaded context. Therefore STM32MP13x
explicitly expects SCMI services based on SCMI/OP-TEE transport, not
SCMI/SMC transport.

Best regards,
etienne

> Cheers,
> Ahmad

>
>>
>>> +            #address-cells = <1>;
>>> +            #size-cells = <0>;
>>> +            linaro,optee-channel-id = <0>;
>>> +            shmem = <&scmi_shm>;
>>> +
>>> +            scmi_clk: protocol@14 {
>>> +                reg = <0x14>;
>>> +                #clock-cells = <1>;
>>> +            };
>>> +
>>> +            scmi_reset: protocol@16 {
>>> +                reg = <0x16>;
>>> +                #reset-cells = <1>;
>>> +            };
>>> +        };
>>> +    };
>>>       clocks {
>>>           clk_axi: clk-axi {
>>>               #clock-cells = <0>;
>>
>


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