[U-Boot] [PATCH 1/3] [RFC] Add support for early serial debugconsole

[Ken.Fuchs at bench.com]

> It's weekend, and not many people are active now. Let's  wait  for  a
> few  more  days  if  anybody  shows  up with arguments to support your
> patches.

In my opinion, the serial device should be the first device
initialized and utilized before all other devices where that
is possible.  For example, it would be very useful to have
serial output while debugging RAM initialization.  An early
serial port prior to U-Boot relocating itself would be very
useful for porting U-Boot to new boards.

An early debug serial port would be a good candidate for
mainline U-Boot:

CONFIG_DEBUG_EARLY_SERIAL has been implemented in a few forks
of U-Boot.

I also favor an early serial debug console as advocated by this
patch, but perhaps its code should be self contained.  I'm not
sure it is a good idea to modify some commands so they can be
run before RAM relocation.  If such a thing can be done simply,
it should be done for all commands.

Is the patch submitted clean enough?  No, the implementation
could be improved with some effort; a few #if - #else - #endif
clauses could be eliminated for example.

Would an easier to maintain implementation even be feasible?

I agree that a JTAG debugger is extremely useful for board
bring-up, but they are very expensive.

I'm strongly in favor of having some early serial functionality
whether in the form of simply being able to send output to the
serial port or having a semi-functional to fully functional shell
prior to RAM relocation.

Sincerely,

Ken Fuchs