[Lenny400] LetuxOS on SD card for MIPS JZ4780 CI20

Paul Boddie paul at boddie.org.uk
Sat Apr 13 21:48:05 CEST 2019


Nikolaus,

On Saturday 13. April 2019 20.02.15 H. Nikolaus Schaller wrote:
> 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 ...

The details certainly look quite reasonable.

> 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/

I noticed that the CONFIG contains settings enabled for ARM/OMAP and wondered 
whether this was actually the configuration used.

[...]

> 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"

What is the SPL? I don't remember ever seeing anything before those messages. 
One thing which I did encounter was some confusion about which UART was being 
used. Ultimately, I used UART0, but I do wonder if U-Boot might use another 
UART early on.

Here is a page on the topic:

https://www.elinux.org/CI20_Headless_Setup

What I did need to do was to change /etc/inittab to enable ttyS0 for a login 
prompt to appear on UART0, but that is with the kernel starting...

> 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)

I don't know what Multiarch means in this context, but I would think that just 
bundling the right device tree binary would be enough. Otherwise, the SoCs are 
pretty similar, and I can't immediately think of anything that would require 
different kernels for the different devices, at least if device tree works as 
advertised.

Still, this looks promising!

Paul


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