On 06/29/2011 11:06 PM, Somebody in the thread at some point said:
Hi -
Btw I don't yet fully understand Panda boot architecture. This X-Loader
appear to come from SD card. But what boots it then? How that piece is
called, where it comes from, how it should be upgraded, and is that
ever needed? I found this:
https://gforge.ti.com/gf/project/omapzoom/wiki/?pagename=BootingAndFlashing
but it's still a bit confusing (like, doesn't name that first loader,
and from OS perspective, it appears to be 3-stage boot).
Nicolas already gave a rundown but the short answer is the ROM can drive
the MMC hardware of the OMAP4, talk SD-HC protocol, parse your partition
table and FAT filesystem on your SD Card, and will load and execute a
file of the magic name "MLO" on partition 1.
That is "x-loader", which sets stuff up and loads and executes a magic
file "u-boot.bin" off partition 1. And "u-boot" does its usual thing
from then on.
ROM being ROM, it can't be upgraded, however, unlike in OMAP3 the ROM in
OMAP4 stuff seems pretty much perfect for SD Card boot case, it doesn't
care about any arcane stuff like geometry for example. It only needs to
success to pull MLO reliably and anything further can be done there in
an upgradeable way.
Of course, it'll pull anything called MLO. I believe folks are working
on adding stuff to be able to call U-Boot "MLO" directly eliminating
x-loader and Matt Hsu and I already did that for Qi.
So, it would be nice if you could suggest Android team which
repo/branch/tag/revision can be safely used to produce releases.
Yeah confusing ain't it. There are two camps in x-loader development
one on omapzoom and one on gitorious. TI engineers like omapzoom but
the official repo is gitorious.
The magic branch I (and I believe Ubuntu) use is:
git://gitorious.org/x-loader/x-loader.git master
... and BTW, 3.0 android kernel from us requires MLO update from what
you supply at the moment to this in order for 3D unit to start up. So
this is a good idea anyway.
-Andy
--
Andy Green | TI Landing Team Leader
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