Date: Tue, 05 Sep 2006 11:41:52 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: andre@freebsd.org Cc: freebsd-arm@freebsd.org Subject: Re: ARM boot process Message-ID: <20060905.114152.-399282970.imp@bsdimp.com> In-Reply-To: <44FDAE15.1010400@freebsd.org> References: <44FC3626.701@freebsd.org> <20060904.115205.-626772610.imp@bsdimp.com> <44FDAE15.1010400@freebsd.org>
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In message: <44FDAE15.1010400@freebsd.org>
Andre Oppermann <andre@freebsd.org> writes:
: M. Warner Losh wrote:
: > In message: <44FC3626.701@freebsd.org>
: > Andre Oppermann <andre@freebsd.org> writes:
: > : I'm new to the embedded system world and have got some Atmel
: > : at91rm9200 eval boards I'm playing with. Most of them came
: > : with Linux and some boot loader to it.
: > :
: > : The supplied boot loaders can't load a FreeBSD arm kernel and
: > : complain about wrong magic.
: >
: > Which kernel were you using?
:
: After I sent the original email I tried a couple of things and got
: some help on developers IRC as well (missing you there lately).
:
: What I did was to check out the arm tree from p4 and do a 'make
: TARGET_ARCH=arm kernel-toolchain' followed by a 'make TARGET_ARCH=
: arm KERNCONF=KB920X buildkernel'. The KB920X is modified such that
: it includes the hints.at91rm9200. One step I somehow did but can't
: reproduce today was the 'make trampoline' target. Every time and way
: I try it now fails in elf_trampoline.c because it doesn't have proper
: sys/* includes as seen from the kernel compile directory. There I'm
: stuck right now. The kernel from yesterday successfully boots on the
: KB9202 and mounts root over NFS. The loader is the super-primitive
: one that comes with the board. I'm setting mac, ip and tftp server
: address, do the tftp download to 0x20000000 and start from that address.
OK.
: What I've got no clue yet is how to build a MFS image that gets fused
: with the kernel so I may skip NFS and boot with only TFTP or even put
: it on flash.
I've done that, but I'll have to check my notes. I've use mkfs to
creaet the ramdisk image, and then frobbed some knob in the config
file to included when I built kernel.tramp.
: > boot0* is to bootstrap the board. boot0 lets you load an arbitrary
: > program to execute. boot0iic allows you to load an image to put in
: > the iic eeprom (maybe on only on the KB9202). boot0spi allows you to
: > load an image into the SPI part.
: >
: > bootiic is usually what you put in the iic part to boot. It's fully
: > functional. If you have different eeprom parts, you'll need to tweak
: > it.
:
: OK, this looks pretty much like the Kwikbyte loader.
Except that it works... :-) There's lots of bugs in the kwikbyte
loader.
: > bootspi is what I put in the SPI part. It is presently optimized for
: > the part that I have, and might need some tweaks.
: >
: > bootsd will boot off a SD card. It doesn't quite work yet, there's
: > some unaligned accesses that I'm still working on sorting out...
:
: SD is the interesting part. ;-)
:
: I included the qdmmc driver in my working kernel as well but it fails
: to detect an inserted SD (1GB) or MMC (16MB) card. How does the IO pin
: setup on the AT91RM9200 work? Where are the IOs assigned to the functions?
Chances are good that the I/O stuff isn't configured correctly. We're
getting close to the point of needing different I/O config for
different boards. All that's done right now in kb920x_machdep.c. In
an ideal world, the boot loader would pass us a board type (I think it
may already), we'd save it (which we don't right now) and then use it
later to do board specific things.
: > : For the at91rm9200 a number of boot loaders are in boot/arm/
: > : but so far I haven't figured out which one to use. Eventually
: > : I'd like to have it boot from the SD card.
: >
: > That's not yet in the tree. I'm working on booting off a UFS
: > partition.
:
: Perfect.
:
: > I've not looked at integrating the SD support with things like redboot
: > or uboot yet.
:
: What does boot2 do? And how can I boot an ARM kernel w/o doing the
: trampoline step? Is that possible at all?
boot2 doesn't do anything. bootsd is a copy of boot2 that's been
augmented to be the only stage.
I don't think that we've investigated getting /boot/loader working
on the arm. With that, we'd not need the trampoline stuff at all.
That's there to trick the kernel into thinking it was booted with
/boot/loader.
My bootsd code won't care...
I'm not sure what this has to do with redboot or uboot support. There
I think one would have to boot off a ext2fs partition.
: Once I'm up to speed and familiar with ARM/AT91RM9200 I'm ready to help
: on improving it. The devices/ports I'll primarily care about and will
: use are SPI, TWI, 8bit parallel bus, SD/MMC, SSC, EMAC.
Same for us, except not parallel bus.
Warner
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