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

[Srinivas Kandagatla]

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?