[Uboot-stm32] [PATCH v2 2/5] arm: stm32mp: handle the OP-TEE nodes in DT with FIP support

[Patrick DELAUNAY]

Hi Ahmad

On 7/15/21 7:11 PM, Ahmad Fatoum wrote:
> Hello Patrick,
>
> On 15.07.21 17:22, Patrick Delaunay wrote:
>> With FIP support in TF-A (when CONFIG_STM32MP15x_STM32IMAGE
>> is not activated), the DT nodes needed by OP-TEE are added by OP-TEE
>> firmware in U-Boot device tree, present in FIP.
> What about the SCMI nodes. Who will fix up those?


In downstream, we don't have issue, as only SCMI clock are supported 
with TF-A (with or wihtout OP-TEE).

In latest delivery = OpenSTLinux V3.0, we modifed the STM32MP15 device 
tree of U-Boot

and Linux kernel to use these SCMI clocks by default.

We keep the backward compatibility only in U-Boot the basic boot (=boot 
with SPL and wihout TF-A).

For STMicroelectronics delivery the SCMI support don't need to be 
dynamically handle as it is now mandatory,

it is not linked to the FIP support or to the presence of OP-TEE,

but is it linked to power management support.


Today we have issue only for upstream: we need to continue to support DT 
without SCMI clocks.

and we don't have a clear solution... so SCMI clocks support is not yet 
upstreamed in DT side

(but upstreamed in drivers).


I have a prototype to allow overlay at U-Boot level as proposed by Marek:

TF-A BL2 found in the FIP a U-boot generic device tree and a SCMI overlay

=> U-Boot apply this overlay at boot before to parse its DT.


It is working but the boot time is impacted (5 seconds without data 
cache management

update and still 270 ms with dirty a dirty patch to activate data cache 
before apply overlay)


But 270 ms for U-Boot's DT overlay +  270ms for kernel's DT overlay is 
not acceptable

and SCMI upstream is suspended for STM32MP15x.


>
>> These nodes are only required in trusted boot, when TF-A load the file
>> u-boot.stm32, including the U-Boot device tree with STM32IMAGE header,
>> in this case OP-TEE can't update the U-Boot device tree.
> [snip]
>
> Cheers,
> Ahmad
>
>

Regards

Patrick