Re: [Linux-stm32] [PATCH v2 00/14] Introduce STM32MP1 RCC in secured mode

[Ahmad Fatoum]

Hello,

On 11.03.21 16:18, Alexandre TORGUE wrote:
>> I raised this issue before with your colleagues. I still believe the correct way
>> would be for the TF-A to pass down either a device tree or an overlay with the
>> actual settings in use, e.g.:
>>
>>    - Clocks/Resets done via SCMI
>>    - Reserved memory regions
>>
>> If TF-A directly boots Linux, it can apply the overlay itself, otherwise it's
>> passed down to SSBL that applies it before booting Linux.
> Discussing with tf-a and u-boot guys, this solution could imply hard synchronization between tf-a/u-boot. The most simple remains a "secure" dts.

OP-TEE can be configured via CFG_EXTERNAL_DTB_OVERLAY to pass
along an overlay that describes the reserved memory regions it uses.

A similiar approach could work here. The only synchronization you need
in Linux is to keep phandles that the overlay can reference.

Cheers,
Ahmad

> 
> regards
> Alex
> 
>> Cheers,
>> Ahmad
>>
>>>
>>> Gabriel, can you wait a bit before sending something about SCMI in dtsi, I would like to align this strategy internally.
>>>
>>> Marek, Alex: thanks for your inputs.
>>>
>>> Regards
>>> Alex
>>>
>>>>> The third could be the less costly.
>>>>
>>>> [...]
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>>
> 

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