[Lenny400] LetuxOS on SD card for MIPS JZ4780 CI20

[H. Nikolaus Schaller]

Hi Paul,
I have spent some minutes on adapting LetuxOS to the CI20 so that we eventually can create bootable SD cards with "makesd".

I have a first success:

Net:   dm9000
Hit any key to stop autoboot:  0 
4058380 bytes read in 673 ms (5.8 MiB/s)
## Booting kernel from Legacy Image at 88000000 ...
   Image Name:   Linux-4.19.34-letux-l400+
   Image Type:   MIPS Linux Kernel Image (gzip compressed)
   Data Size:    4058316 Bytes = 3.9 MiB
   Load Address: 80010000
   Entry Point:  8065f750
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK

Starting kernel ...

This is a self-made cross-compiled SPL + U-Boot on SD card based on the description
at https://elinux.org/CI20_Dev_Zone#Building_uboot_from_sources

	http://download.goldelico.com/letux-u-boot/CI20/2019-04-13/

This can now be installed easily by the updated "makesd ci20". It is already prepared to load the
latest stable/longterm kernel and currently the old Letux 400 Lenny rootfs (I have not spent time to
cross-debootstrap a newer one).

I can break into the u-boot console and print the environment:


Hit any key to stop autoboot:  0 
ci20# printenv
baudrate=115200
board_date=20150803
board_mfr=NP
bootargs=console=ttyS4,115200 console=tty0 mem=256M at 0x0 mem=768M at 0x30000000 rootwait quiet rw root=/dev/mmcblk0p1
bootcmd=run ethargs; ext4load mmc 0:1 0x88000000 /boot/uImage; bootm 0x88000000
bootdelay=1
ethact=dm9000
ethaddr=d0:31:10:ff:6e:86
ethargs=env set bootargs ${bootargs} dm9000.mac_addr=${ethaddr}
loads_echo=1
serial#=4217
stderr=eserial0,eserial4
stdin=eserial0,eserial4
stdout=eserial0,eserial4

Environment size: 488/32764 bytes
ci20# 

There are two issues so far:

1. the console output of the SPL (and U-Boot) seems to be mostly missing and starts
   not before the "Net:   dm9000" line or "Hit any key"
2. Kernel is not starting
   well, I have not found how this U-Boot wants to handle the device-tree so this is very expected.
   And I am not 100% sure if the installed kernel is the jz4730/Mipsbook or the jz4780/CI20 kernel
   (unfortunately, there is no Multiarch for Ingenic so we can't build universal kernels)

Best regards,
Nikolaus