How to get UART_1 to work on M7 core during U-Boot?

[kawin]

Since U-Boot initializes its own clock, this causes UART_1 outputs random characters when transmitting. How do I make UART_1 work when using U-Boot to start M7 baremetal firmware? I'm trying to run A53 Linux and M7 firmware apps at the same time.

[bpe]

There is a software package called Platform Software Integration that offers
an demo running u-Boot on A53 and a bare metal application on an M7 core in parallel.
The Lighting M7 demo that is part of the package does exactly what you want -
it utilizes one of UARTs to interact with the user independently of u-Boot.
Use the demo as a reference. More information can be found in the
documentation distributed with the package. For more questions about Platform
Software Integration demos, specific techniques it uses to initialize the peripherals
so that they do not collide with other cores/demo components and other related
questions, post in this Forum. It offers a shorter path to the  demo owner SW
team.

Platform Software Integration package is available via online Automotive
Software Package Manager.

Best Regards,
Platon