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

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Message-ID: <4e4bb5eb-54af-f6aa-6c77-f54d03fd7323@pengutronix.de>
Date:   Thu, 11 Mar 2021 16:49:09 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Alexandre TORGUE <alexandre.torgue@...s.st.com>,
        Marek Vasut <marex@...x.de>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "Alex G." <mr.nuke.me@...il.com>,
        Gabriel FERNANDEZ - foss <gabriel.fernandez@...s.st.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Etienne CARRIERE <etienne.carriere@...com>
Cc:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [Linux-stm32] [PATCH v2 00/14] Introduce STM32MP1 RCC in secured
 mode

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.
>>>>
>>>> [...]
>>> _______________________________________________
>>> Linux-stm32 mailing list
>>> Linux-stm32@...md-mailman.stormreply.com
>>> https://st-md-mailman.stormreply.com/mailman/listinfo/linux-stm32
>>
> 

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