[E3-hacking] PBL and flash access on the E3

David Given dg at cowlark.com
Thu Mar 30 00:28:53 BST 2006

Jonathan McDowell wrote:
> It won't run more than a 16K block, which is too small for u-boot. I
> think it might run a bigger compressed block (LDR is bigger, for
> example), but I'm not quite sure it'll stretch to the 80 or so K my
> current u-boot image is.

That's annoying, but I think we understand enough of the PBL entrypoints to
write a quick and dirty bootstrap loader that's enough to boot u-boot.

>> (Also, you may be interested to know that the kernel seems to be
>> ignoring the boot parameters passed to it by u-boot.)
> Really? It picks them up fine for me. If I do:
> setenv bootargs mem=32M console=ttyS0,115200n8 root=/dev/ram0 initrd=0x11c00000,4M
> bootm 11d00000

Yes, I was using the wrong syntax --- setenv bootargs=..., which appears to
work, but just does the wrong thing.

I now have it working fine, using a USB mass storage device as its root
filesystem! The only gotcha is that the kernel doesn't understand /dev/sd?
naming, so you have to use root=8:1.

I've been experimenting with various off-the-shelf ARM root filesystems,
more out of interest to see what would happen than any real expectation
that it would work. Yours works, of course. A Familiar GPE install image
doesn't, unfortunately; it seems to hang immediately after mounting the
root filesystem. (This was after I repacked the JFFS2 image as an ext2
image.) I tried again with init=/bin/sh, but that hung too.

A Debian unstable initrd (stable won't work because of the 2.6 kernel), to
my total surprise, actually runs fine! It complains bitterly about having
to go into low-memory mode, but it ran, with dialogues and everything, up
to the point where it was trying to download package files. I currently
don't have any networking, but I think I'll try to scrounge a USB ethernet
dongle and see what happens.

debian-installer claims to use about 8MB in low-memory mode, with about
20MB free. It's very sluggish over the serial port, but much snappier on
the real console (Debian looks *weird* on that little screen).
Unfortunately the mailboard's not working yet, and there aren't enough keys
on the main keypad to interact with debian-installer.

I'm disappointed and a bit puzzled that Familiar wouldn't work. It would be
far more suitable than Debian, and I reckon most of the hardware
functionality is there to run GPE or Opie. I don't know what's going wrong.
I'll have to investigate that tomorrow.

ADDENDUM: I've figured out the keymap on the keypad; the important keys are
VIDEO (which is RETURN) and MOBILE MSG (which is BACKSPACE). This means I
can now make debian-installer work sufficiently to allow me to get to a
shell and enter commands. It feels weird.

+- David Given --McQ-+ "If you're up against someone more intelligent
|  dg at cowlark.com    | than you are, do something insane and let him think
| (dg at tao-group.com) | himself to death." --- Pyanfar Chanur
+- www.cowlark.com --+

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