[Lenny400] LetuxOS on SD card for MIPS JZ4780 CI20

[Paul Boddie]

On Thursday 18. April 2019 19.17.12 H. Nikolaus Schaller wrote:
> > Am 18.04.2019 um 19:08 schrieb Paul Boddie <paul at boddie.org.uk>:
> > 
> > https://github.com/MIPS/CI20_u-boot
> > 
> > Branch ci20-v2013.10 from the above repository.
> 
> Yes, exactly.

Good to know that we're still on the same page. :-)

[...]

> Most likely... But how should we run a device-tree kernel now?

I imagine that any future effort would depend on doing so.

> It does not look as if there is a MIPS pendant to CONFIG_ARM_APPENDED_DTB.
> Android seems to have that:
> 
> https://android.googlesource.com/kernel/goldfish.git/+/ffe2e9528580222567114
> 0560e4261425f63db69%5E!/
> 
> Well, there is always the option to manually do the append. But I am not
> sure if the MIPS kernel is searching for it...

Is this it...?

CONFIG_BUILTIN_DTB=y

I vaguely remember similar options when doing the initial work for the Letux 
400, or maybe it was related to the Ben NanoNote and newer kernels. Maybe 
these:

CONFIG_MIPS_NO_APPENDED_DTB
CONFIG_MIPS_ELF_APPENDED_DTB
CONFIG_MIPS_RAW_APPENDED_DTB

Of course, I did spend some time trying to define a usable device tree for the 
Letux 400, and I am pretty sure that the NanoNote kernel adopted device tree.

Plus, there are device tree files for the JZ4780 and CI20, so I do wonder 
whether the support isn't already in place. So, maybe a perusal of the CI20 
discussion groups/lists is needed to remind myself.

> Or should we backport a newer bootm command? That may not be easy as it
> assumes a standard to pass the DTB address to a kernel and that might not
> be in the old tree.
> 
> So we are a little stuck here. Ideas are welcome!

I would need to refresh my memory a lot more to be able to say something 
sensible, I think.

Paul