U-Boot SPL doesn't consistently print on boot

[pamolloy]

This has been a long standing issue. When I looked into it last year it seemed like the driver model within U-Boot led to the UART being initialized after logs were printed. Either way, in most cases booting over JTAG and SPI flash it doesn't print anything.

[ozan956]

There is an interesting behavior.

This is something that I encountered by mistake. If you put some timeout when initializing the gdb client with:

-l timeout
Set the timeout (in seconds) of any communication used by gdb for remote debugging

The U-Boot SPL logs can be achieved.

GDB not says too much on what is the behavior of the timeout, so how it fixes the problem is unclear.

Link: https://sourceware.org/gdb/current/onlinedocs/gdb#index-remote-timeout