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

[Marek Vasut]

On 3/11/21 9:08 AM, Alexandre TORGUE wrote:
> Hi ALex

Hello everyone,

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> > Subject: Re: [PATCH v2 00/14] Introduce STM32MP1 RCC in secured mode
> >
> > On 1/26/21 3:01 AM, gabriel.fernandez@xxxxxxxxxxx wrote:
> > > From: Gabriel Fernandez <gabriel.fernandez@xxxxxxxxxxx>
> > >
> > > Platform STM32MP1 can be used in configuration where some clocks and
> > > IP resets can relate as secure resources.
> > > These resources are moved from a RCC clock/reset handle to a SCMI
> > > clock/reset_domain handle.
> > >
> > > The RCC clock driver is now dependent of the SCMI driver, then we have
> > > to manage now the probe defering.
> > >
> > > v1 -> v2:
> > >     - fix yamllint warnings.
> >
> > Hi Gabriel,
> >
> > I don't have much clout with the maintainers, but I have to NAK this series
> > after finding major breakage.
> >
> > The problem with series is that it breaks pretty much every board it touches.
> > I have a DK2 here that I'm using for development, which no longer boots with
> > this series applied.
> >
> > The crux of the matter is that this series assumes all boards will boot with an
> > FSBL that implements a very specific SCMI clock tree. This is major ABI
> > breakage for anyone not using TF-A as the first stage bootloader. Anyone
> > using u-boot SPL is screwed.
> >
> > This series imposes a SOC-wide change via the dtsi files. So even boards that
> > you don't intend to convert to SCMI will get broken this way.
> > Adding a -no-scmi file that isn't used anywhere doesn't help things.
>
> You are right. We mainly take care about NO ST (DH/...) boards, but  not really about current usage
> Of our stm32 boards. Several options exist:

Since a lot of people benefit from the good upstream support for the MP1 
_and_ keep updating their machines to get the latest fixes, it is very 
important to keep the current usage working.

> 1- Break the current ABI: as soon as those patches are merged, stm32mp157c-dk2.dtb will impose to use
> A tf-a for scmi clocks. For people using u-boot spl, the will have to create their own "no-secure" devicetree.

NAK, this breaks existing boards and existing setups, e.g. DK2 that does 
not use ATF.

> 2-As you suggest, create a new "secure" dtb per boards (Not my wish for maintenance perspectives).

I agree with Alex (G) that the "secure" option should be opt-in.
That way existing setups remain working and no extra requirements are 
imposed on MP1 users. Esp. since as far as I understand this, the 
"secure" part isn't really about security, but rather about moving clock 
configuration from Linux to some firmware blob.

> 3- Keep kernel device tree as they are and applied this secure layer (scmi clocks phandle) thanks to dtbo in
> U-boot.

Is this really better than
#include "stm32mp15xx-enable-secure-stuff.dtsi"
in a board DT ? Because that is how I imagine the opt-in "secure" option 
could work.

> The third could be the less costly.

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