Dear Wolfgang Denk,
Well, you can provide measures for a reset to a sane state, then.
This sounds even more complicated to me. In fact - I don't have any clue, what and howto measure and reset the environment. This system doesn't even had a reset buttom... so it is always a cold boot.
I don't have any connection to uboot at all, as in my final system there is no serial interface to change it back.
You could eventually use netconsole.
Netconsole requires (afaik) a linux kernel, that is working.
If just the environment is hosed, it would be sufficient to provide some means to perform a "manufacturer reset" and restore the environment to a known good state. You could - for example - act on certain key presses / key combinations when the board is reset/powered on. Several boards do that.
I would do so, in fact that was my first idea. But I just have network, nothing else. But here I am at the beginning. How to listen on a network port ( I know what to don in linux, but in uboot?) and howto make this change in uboot environment to a certain state. (this can boot a system via tftp then instead of a flash file system)
Best regards Steffen