Hi ST Dev team!
I have found that LSE is mandatory when building a new custom board. If not LSE is mounted and configured, then both TF-A and Op-tee will complaining about clock ID 5, which is LSE.
Here is a walk around for Op-tee by removing the &clk-lse.
https://github.com/DanielMartensson/Watermelon-Wine-1A/blob/linux-testing/watermelon-wine-os%2Fcubemx%2FCA35%2FDeviceTree%2Ffirmware%2Foptee-os%2Fstm32mp257f-firmware-mx.dts#L497-L498
And for TF-A, ut must need some modification inside the code:
https://github.com/evildeeds/meta-watermelon-wine-stm32mp/blob/656727dfcfb62cffbcd6aaec07fc4dfc55024a75/recipes-bsp/trusted-firmware-a/tf-a-stm32mp/clk-stm32-core.c#L462-L465
Processor: STM32MP257F
STM32MP151AAC3 custom board with STM32-OS as operating system: https://github.com/DanielMartensson/STM32-Computer
STM32MP257FAK3 custom board with STM64-OS as operating system: https://github.com/DanielMartensson/STM64-Computer
