On 3/11/21 12:10 PM, Alexandre TORGUE wrote:

Hi Guys

On 3/11/21 5:11 PM, Marek Vasut wrote:

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On 3/11/21 3:41 PM, Ahmad Fatoum wrote:

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Hello,

Hi,

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On 11.03.21 15:02, Alexandre TORGUE wrote:

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On 3/11/21 12:43 PM, Marek Vasut wrote:

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

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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.

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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.

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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.

Discussing with Patrick about u-boot, we could use dtbo application 
thanks to extlinux.conf. BUT it it will not prevent other case (i.e. 
TF-A which jump directly in kernel@). So the "least worst" solution 
is to create a new "stm32mp1257c-scmi-dk2 board which will overload 
clock entries with a scmi phandle (as proposed by Alex).

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.

That sounds good and it is something e.g. R-Car already does, it 
merges DT fragment from prior stages at U-Boot level and then passes 
the result to Linux.

So on ST hardware, the same could very well happen and it would work 
for both non-ATF / ATF / ATF+TEE options.

Even this solution sounds good but we are currently not able to do it in 
our TF-A/u-boot so not feasible for the moment. So we have to find a 
solution for now. Create a new dtb can be this solution. Our internal 
strategy is to use scmi on our official ST board. It will be a really 
drawback to include a "no-scmi.dtsi" in DH boards (for example) and to 
create a stm32mp157c-noscmi-dk2.dts ?

It could work, as long as all users are reminded to change their build 
scripts to pick up a "-noscmi.dtb". I suspect that if this were the case 
we'll see quite a few bug reports saying "stm32mp1 no longer boots with 
kernel v5.13".

I didn't think of this originally, though u-boot already does the DTB 
patching for OPTEE reserved memory regions. It's not too hard to also 
patch in the SCMI clocks at boot. In u-boot's case, runtime detection 
might even be feasible.

Alex