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

Wolfgang Denk wd at denx.de
Wed Mar 21 23:52:20 CET 2012

Dear Stephen Warren,

In message <4F6A01D3.3020506 at wwwdotorg.org> you wrote:
> > It appears that all you are trying here is an annoying, but somewhat
> > unlikely error situation.  As marked above (see *), it might make
> > sense to think of alternative ways to find out what the console port
> > might be.  One possibility to do this is to use the environment.
> > You need access to the environment anyway to initialize the console
> > port (for reading the "baudrate" setting).  So why not encoding the
> > console UART port for example as part of a "hwconfig" setting?  This
> > setting could be auto-initialized when you load a DT on this board
> > (eventually after verifying that it works).
> I'd prefer to just have a different U-Boot (build) config for each HW
> configuration, and define the console UART as part of that configuration
> using the existing defines that are for that purpose.

This is another option - at the cost of maintaining separate binary

> If we put the UART ID into the environment, then we either need to:
> a) Have a different U-Boot configuration anyway, in order to define the
> different environment during the U-Boot build process.
> b) Post-process the U-Boot binary after building it, in order to modify
> the environment that's contained in that binary.

Not true.  In the normal course of events, the board would boot with a
working device tree provided, which provides correct console
information.  This could be used to auto-initialize the correct
environment settings.  You just have to make sure that board boots a
single time with a working DT image - I don't know how production
tests and/or software commissioning on these boards is organized, but
this seems to be a possible route to me. [Been there, done that
before.  About 12 years before, IIRC.]  You probably also need to
program MAC addresses etc. ?

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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