[Lenny400] LetuxOS on SD card for MIPS JZ4780 CI20

[H. Nikolaus Schaller]

> Am 18.04.2019 um 19:08 schrieb Paul Boddie <paul at boddie.org.uk>:
> 
> On Thursday 18. April 2019 18.25.36 H. Nikolaus Schaller wrote:
>> 
>>>> (nc)	red	USB +5V - BTW: it should be possible to connect to pin 2/4 and
>>>> power the board through the FTDI USB...
>> 
>> Yes, it works to power the board through the FTDI adapter so that I only
>> need one cable :
> 
> Interesting! This would be quite convenient.
> 
> [...]
> 
>> I spent some more minutes and it looks as if the official u-boot source
>> recommended here
>> 
>> 	https://www.elinux.org/CI20_Dev_Zone#U-Boot
>> 
>> does not support device tree at all. Which U-Boot are you using on SD card?
>> Where did you get it from or how did you build it?
> 
> I guess it's the same thing:
> 
> https://github.com/MIPS/CI20_u-boot
> 
> Branch ci20-v2013.10 from the above repository.

Yes, exactly.

> When I looked into this, I made the quick choice of just fixing up the 
> problems in that code that modern compilers experience (like compiling older 
> Linux kernels)

I have added one patch for Letux cross-compilation:
http://git.goldelico.com/?p=letux-uboot.git;a=shortlog;h=refs/heads/ci20-v2013.10

> rather than trying to introduce CI20 support into the upstream 
> U-Boot. I imagine that the developers just gave up with the upstreaming of 
> changes.

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

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/+/ffe2e95285802225671140560e4261425f63db69%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...

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!

BR,
Nikolaus