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Date:      Thu, 8 Mar 2012 16:24:51 -0800
From:      Juli Mallett <jmallett@FreeBSD.org>
To:        "freebsd-mips@FreeBSD.org" <freebsd-mips@freebsd.org>
Subject:   RouterBOOT on RB450G has a 4MB NAND kernel size limit
Message-ID:  <CACVs6=8o%2B%2BQnDiiFn_nLinNa83sjYSxDNyzEt%2B=Ke14exGnM5Q@mail.gmail.com>

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Hey folks,

I thought it might be useful to share this with others, so they don't
waste 6 hours diffing ELF files trying to figure out what the problem
is.

It turns out that although it can load ELF files of variable size over
TFTP, and although the system is configured with a larger kernel NAND
partition, RouterBOOT seems to choke (without any clear error, mind
you, because that would be gratuitously-sensible) on loading kernels
larger than 4MB.  Of course, it's hard to figure this out because
nothing useful turns up on a quick search for '"setting up elf
image..." hang' or '"setting up elf image..." -"setting up elf
image... ok"', although once you figure it out, it's easy to confirm
with a quick Google along the lines of 'rb450g 4mb kernel'.

So, be warned if you're thinking that you'll use an OpenWRT kernel
with initramfs over netboot to provision devices to use FreeBSD by
copying the kernel to NAND.  Or if you've got yaffs patches to your
kernel and can just copy over kernels with impunity.

Has anyone looked at using U-Boot as a second stage loader on this
hardware?  In order to make loader useful, we'd have to add an awful
lot of infrastructure, including another yaffs implementation, when we
don't even have one in-tree yet.  What would be most useful, too,
would be to have MMC + SPI support in loader (here again, U-Boot is
helpful), so that we could load kernels from SD.  That's a lot of work
on loader, and U-Boot already does it all, right?  Any thoughts?

(There is an MMC-over-SPI driver coming to the tree Real Soon Now, so
booting FreeBSD from these things in production is actually quite
trivial, if you can solve the kernel loading dilemma.)

Yours in frustration with Mikrotik,
Juli.



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