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

[Ahmad Fatoum]

Hello Etienne,

On 16.03.22 12:01, Etienne Carriere wrote:
> 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 at foss.st.com wrote:
>>>>> From: Gabriel Fernandez <gabriel.fernandez at foss.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.

I see. Users can still override it as they see fit and I understand that
ST would prefer to have the "fully-featured" boot chain be the default
for the new SoC. So no concerns from my side.

Thanks a lot for the clarification!

Cheers,
Ahmad

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


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