[U-Boot] [PATCH] omap3: overo: Select fdtfile for expansion board

[Stefan Herbrechtsmeier]

Am 07.06.2014 22:11, schrieb Ash Charles:
> On Sat, Jun 7, 2014 at 10:48 AM, Tom Rini <trini at ti.com> wrote:
>> In this case it might be harder to do this in a shell cmd.  But we
>> _must_ check for fdtfile being unset and only setenv if not already set.
>> And then drop fdtfile from the config file.
> Thanks both for your comments and suggestions.  I agree that fdtfile
> should only be set if it is currently unset---I'll send an updated
> patch.
It would be nice if you only set an environment variable 'expansionname' 
and setup the fdtfile via a command in the environment. This makes sure, 
that under normal condition the fdtfile is not set and thereby not saved 
in the environment with the command saveenv.

> There is actually already a mechanism for environment variables to be
> set by the board eeprom [1][2] so an expansion board could certainly
> set the desired fdtfile name.
At the moment I use this functionality to set the environment variable 
'fdtfile'.

>    The challenge (and my biggest
> motivation for writing the patch) is making sure we select a dtb for
> either 37xx (Overo Storm) or 35xx (non-storm) as otherwise Linux
> doesn't boot.
Maybe you could set an environment variable 'boardname' to 'overo' or 
'overo-storm' and use something like the following environment command:

if test -n \"${boardname}\" && test -n \"${expansionname}\"; then
     setenv fdtfile omap3-${boardname}-${expansionname}.dtb;
fi;

This allows the expansion board to set the expansionname via eeprom and 
works with both overo boards.

>
> --Ash
> [1] http://elinux.org/BeagleBoardPinMux#Expansion_boards
> [2] https://github.com/gumstix/meta-gumstix-extras/blob/dylan/recipes-core/i2c-tools/omap3-writeprom/writeprom.sh