Where is uart4 configured for output on STM32MP157d-dk1

[mjuels]

I am working with an STM32MP157d-dk1 board, but am trying to make my own MVP board running yocto on the STM32MP157 chip and have questions concerning the use of the debug console.

I believe the debugging console for the dev board runs via uart4, and in the schematic of the dev board, I can see that uart4 is relayed through the on-board stm32f103 stlink mcu.

Is there a need to run the uart via a separate mcu, or can I route uart4 so that I may access it directly on my own board?

Where is uart4 configured to capture stdin/stdout etc? I can see in the linux device tree that uart4 is the only uart having "status = "okay";", but where is the configuration made for stream capture, baud rate, etc.?

[Erwan SZYMANSKI]

Hello @mjuels ,
First I put you some links that can highlight some points to you:
https://community.st.com/t5/stm32-mpus-products/write-something-to-console-for-a-m4-program-stm32mp157c-dk2/m-p/235718

https://community.st.com/t5/stm32-mpus-products/enable-m4-log-on-stm32mp1-stm32mp157-dk2-dev-kit/m-p/353135

Secondly, I think that UART4 is a Linux resource by default, and so M4 cortex cannot use it directly. That is why the default configuration is a forward of logs to Cortex A7 (Linux) by remoteproc framework.

If you want to reserve UART4 access to M4, you will need to modify your resource sharing configuration through cubeMX.

Kind regards,
Erwan.