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

[Patrick DELAUNAY]

Hi,

On 11/8/22 11:03, Srinivas Kandagatla wrote:
> On 02/11/2022 10:59, Patrick DELAUNAY wrote:
> > Hi,
> >
> > On 11/1/22 08:26, Srinivas Kandagatla wrote:
> > > On 28/10/2022 15:52, Patrick Delaunay wrote:
> > > > For boot with OP-TEE on STM32MP13, the communication with the secure
> > > > world no more use STMicroelectronics SMC but communication with the
> > > > BSEC TA, for data access (read/write) or lock operation:
> > > > - all the request are sent to OP-TEE trusted application,
> > > > - for upper OTP with ECC protection and with word programming only
> > > >    each OTP are permanently locked when programmed to avoid ECC error
> > > >    on the second write operation
> > > >
> > > > Signed-off-by: Patrick Delaunay <patrick.delaunay@xxxxxxxxxxx>
> > > > ---
> > >
> > > For some reason I pushed this patch without a full review, This is 
> > > now reverted from nvmem-next.
> >
> >
> > Ok
> >
> >
> > > 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.


> > - 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?


yes, as it is the SOC dtsi, I don't want change the IP compatible

but I will handle in this driver probe to be backward compatible: 
detection of OP-TEE presence and SMC/PTA support.


only the STM32MP13 SoC only use the PTA, as we have no backward 
compatibility issue.


I will include this STM32MP15 patch in the serie for V2, it should be 
mode clear for the review.


> --srini
> > I can manage this compatibility by detection in STM32 romem driver if 
> > the booth access are managed in the same driver.
>
>
>
> > This patch can be added in the serie to understood the detection 
> > mechanism.

Regards

Patrick