How to Enable or Disable Debug Console Logs at Runtime Across the Entire Boot Chain

[SatyamKumaR1]

Hi ST Support,

I would like to know whether there is a supported mechanism to enable or disable debug console output at runtime across the entire boot chain, including the following components:

• TF-A (Trusted Firmware-A)
• OP-TEE
• U-Boot
• Linux Kernel
• Root File System (user space)

Use case:

• I connect to the target board through the serial console to monitor boot logs.
• After the system has booted, I access the board over USB SSH.
• From the Linux shell, I would like to execute a command that enables or disables debug messages on the serial console.

My goal is to control the debug console output without rebuilding or reflashing any of the bootloader or firmware components.

Could you please let me know:

1. Is there a supported way to enable or disable debug console output for all boot stages at runtime?
2. If this is not possible, what is the recommended approach to achieve similar functionality?
3. Does ST provide any framework or utility to control console logging across TF-A, OP-TEE, U-Boot, the Linux kernel, and user space?

Thank you for your support.

[Olivier GALLIEN]

Hi ​@SatyamKumaR1 

At first sight we don’t see any global solution

Can you please further elaborate your need ? Why console is a concern ? 

Thanks 

Olivier

 

[SatyamKumaR1]

Hi Olivier,

Thank you for your response.

The reason I am asking is that I would like to control the amount of serial console output during system operation without rebuilding or reflashing the software stack.

My use case is as follows:

• During development, I connect to the board through the serial console to monitor the complete boot sequence (TF-A, OP-TEE, U-Boot, Linux kernel, and user space).
• Once Linux has booted, I typically access the board over USB SSH instead of the serial console.
• At that point, I would like to be able to enable or disable debug messages from the running Linux system so that the serial console can either remain quiet or provide detailed logs when needed.

The motivation is to:

• Once the boards are deployed, I typically access them over USB SSH rather than through the serial console. If an issue is encountered in the field, I would like to enable the debug console remotely, collect the required logs for debugging, and then disable it again once the issue has been resolved.
• I would like to avoid rebuilding or reflashing TF-A, OP-TEE, U-Boot, or the Linux kernel each time I need to change the console logging behavior.
• In deployed systems, I also intend to reuse the same UART for application-specific communication (for example, interfacing with an energy meter or other external peripherals). Therefore, it is important that the boot chain does not continuously output debug messages on that UART during normal operation.

Thank you.