[U-Boot] [PATCH] tegra: Specify debugging serial port at boot.

Wolfgang Denk wd at denx.de
Thu Mar 22 00:00:59 CET 2012

Dear Stephen,

In message <4F6A1D1E.2090607 at wwwdotorg.org> you wrote:
> But the last few messages in this thread have all been about the
> following as far as I'm concerned:
> * The U-Boot configuration defines which single UART to use for the
> initial console.
> * This initial console is registered early enough that almost all
> failures can be reported. In particular, something as non-critical as
> locating and parsing the DT should happen after this initial console is
> registered, so that DT existence/parsing problems can be reported to
> this initial console.
> By non-critical here, I mean that there should be no reason to require
> the DT to be parsed in order for the CPU to boot, and the initial
> UART-based console to be registered. DT parsing shouldn't be attempted
> until this basic level of operation is achieved; it should be be
> required that the DT be parsed for any of that to work.
> * When the DT is parsed later, the console specification from DT
> replaces the initial console.
> With this scheme in place, there surely isn't any need for any kind of
> special-case early putc/puts/printf - wasn't this exactly Wolfgang's point?

Correct, that's what I have in mind.

Actually we already do the same in other situations - for example on
systems with console on LCD, whih becomes available pretty late in
the boot sequence.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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