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Re: Raspberry PI

On Wed, 26 Sep 2012 21:27:06 +0300
Petri Laakso <petri.laakso%asd.fi@localhost> wrote:

> > OLinuXino?
> Yup. I've managed to initialize system to the point where I should
> start to write drivers. Like for interrupt controller and clock module,
> to get clock interrupts running.
I have some experience in device driver hacking. So I can offer my help.

> And sure, simple boot loader also,
How do you boot the system at the moment?
How to compile a kernel from your code and boot it?
(kernel config file, how to prepare a "sb"-file, ...)

> please have a look if you are interested:
I am interrested and I have a commit bit set in the NetBSD CVS
repository. So I can get your code into -current once it reaches some
level of usefullness.

> Have on worked on some code for this SoC, or are just planning?
I am just planing / researching where and how to start. You already did
a lot more then I. i.e. I have not written a single line of code.

What I've done up to now:

- Got Debian running as described here:

- Compiled Linux 3.6, barebox bootloader and imx-bootlets:
Now I have a SD-card that starts barebox, but I still have not tried to
boot anything with barebox. Idea is to use barebox to boot NetBSD.
I don't wane depend on barebox, but it seems to be acceptable in the
first steps of a NetBSD port.

- compiled elftosb2 for NetBSD. (Needs minor patching.)

- Build and tested mxsldr: (Needs minor patching.)
With mxsldr you can boot a OLinuXino Mini via USB. You have to desolder
the boot-mode jumpers on the PCB for "USB boot mode". You need a
special USB A-plug to A-plug cable. (Just connect GND, D+ and D- 1:1,
don't connect Vcc.) Power up OLinuXino Mini, connect it to your PeeCee
with the special USB-cable. The OLinuXino Mini now shows up as a
USB-HID device. You need to patch the kernel of your PeeCee to not
attach uhid(4) to this device. Then run mxsldr. It will feed a
"sb"-file to the iMMX233 via USB and the iMMX233 will boot this image.
I tested this with a pre-compiled Linux-kernel. Very hady for testing
kernels without bootloader. You can not do this with the Mini or Maxi,
as they have a USB-hub connected to the USB controller of the iMMX233.

I still have to resarch how this SoC boots. What I found up to now:
- The in-chip ROM loads a "sb"-file from SD-card, USB, NAND-flash, ...
- This "sb"-file contains "imx-bootlets" and a bootloader / kernel.
- The bootlets provide some magic low level hardware initialization.
- The bootlets hand over control to a second stage bootloader / kernel.



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