[U-Boot] Configuring U-Boot through device tree (was: Minutes from the U-Boot Mini Summit 2013)

[Dirk Behme <dirk.behme@gmail.com>]

Am 27.10.2013 18:07, schrieb Detlev Zundel:
...
> ** Configuring U-Boot through device tree
> - _What_ should be configured?
> - Google requires every new U-Boot driver to be configured through
>    device tree in U-Boot
> - Configuring U-Boot through device trees shall aim for using the
>    exact same tree from the Linux kernel.

At ELCE, I attended the Barebox presentation. One Barebox feature 
presented there was "Configure Barbox through device tree". So the 
Barebox people seem to have this already running for some selected 
boards. After their presentation I asked them "how do you decide which 
parts are configured in the boot loader, and which in the kernel, 
then?". And got the quick answer "in doubt, the configuration is done 
two times".

Do we really want this?

If we use the same device tree for U-Boot and the Linux kernel (which 
most probably makes sense) do we really want to do the initialization 
part we do already in U-Boot again in the kernel?

I'm thinking about pin mux or clock settings described in the device 
tree, which are need to get the U-Boot drivers working. If these are 
done two times, then, what's about the risk of clock or pin glitches 
doing the same configuration in the kernel a second time?

Do we need a mechanism to do some configuration only at one place? Or 
isn't there any risk and we can do the same configuration two times? 
What do you think?

Best regards

Dirk