linux-kernel - Re: [PATCH 3/3] nvmem: stm32: add OP-TEE support for STM32MP13x

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Date:   Wed, 9 Nov 2022 18:02:58 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Patrick DELAUNAY <patrick.delaunay@...s.st.com>,
        Alexandre TORGUE <alexandre.torgue@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:     Etienne CARRIERE <etienne.carriere@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Subject: Re: [PATCH 3/3] nvmem: stm32: add OP-TEE support for STM32MP13x



On 09/11/2022 17:35, Patrick DELAUNAY wrote:
>>>
>>>
>>>>
>>>> Why not add TEE client based new driver instead of ifdefing around 
>>>> this driver? Also I see there is not much common across both drivers 
>>>> anyway.
>>>
>>>
>>> I hesitate between the 2 solutions. I choose this update to handle 
>>> the STM32MP15 support with OP-TEE.
>>
>> How are you to handing this?
>>
>>>
>>> For backward compatibility reason the same driver STM32 ROMEM 
>>> associated to compatible "st,stm32mp15-bsec" should be kept.
>>>
>>> - the lower OTP can directly accessible by Linux (the IP is not 
>>> secured) => boot with SPL
>>
>> Can we determine this at runtime?
> 
> 
> Not directly with IP register, but we detect the OP-TEE support at runtime.
> 
You mean using CONFIG_OP_TEE ?


> 
>>
>>>
>>> - the upper OTP and the write operation are requested by 
>>> STMicroelectronics SMCs
>>>
>>>     => boot with TF-A SPMIN and old OP-TEE (before migration to STM32 
>>> BSEC PTA)
>>>
>>>
>>> But in the future OP-TEE the access to OTP should be also done with 
>>> STM32 BSEC PTA...
>>
>> Given that we have only one compatible for these two type of 
>> combinations how are you planning to deal with both the cases and 
>> still be backward compatible?