Leonard Ye wrote:
> 1) bootldr + ramdisk. The ramdisk will be unpacked into DRAM at boot
> time. Such method wastes a lot of DRAM and makes writing back to
> flash diffcult.
I tend to use this one most often if I'm doing kernel development,
because until I figure out some trick to speed up JFFS replays,
unpacking a 3MB ramdisk is actually faster than replaying a 30MB log
during boot. If you want to use an ext2 ramdisk, I would direct you to
the patch I announced on this list a few days ago, as the Compaq code
does not copy ext2 ramdisks to the expected location by default. (The
patch introduces a bootldr param which allows you to specify the correct
location, which is 0xc0800000.)
> 2) bootldr + standard filesystem on flash block device (e.g. M-System
> FTL). So far, nobody had discussed this method in this list. So I
> guess it is not applicable or not feasible.
It's mostly not desirable. Standard filesystems are somewhat
indiscriminate in their use of the storage media, whereas with flash
it's important to minimize the number of block erase actions performed.
> 4) bootldr + MTD + JFFS. This is the best combination. No DRAM is
> wasted and the filesystem can be updated on-the-fly.
I'm quite fond of this one, although I should say that version 1 JFFS is
not especially conservative in its use of storage space (no
compression). As Jamey mentioned, there is already a binary image of a
bootldr on my Assabet page which will do this for you. Since you're
using Neponset, and presumably want to use your SA-1111, I'll caution
you that the binary (and the 26-November patch) has a bug involving the
static memory timings which has been fixed in the latest snapshot patch.
(But since I've temporarily turned off JFFS support for Assabet in the
latest patch, this is of limited value to you. If you proceed down this
path and find that you've hit the SA-1111 limitation, I can walk you
through the correction.)
> args= noinitrd root=/dev/mtdblock4 init=/linuxrc console=ttySA0
Unless this has changed recently, I don't think the Assabet kernel
configuration even picks up kernel params passed by the bootloader. You
can change this in linux/arch/arm/mach-sa1100/arch.c, if you desire.
> linuxEntryPoint=C0008000
> Booting Linux image
I didn't see any message in there about copying the ramdisk from flash
to SDRAM. Check the value of the bootldr param "copy_ramdisk" (should be
1). Of course, after you set that flag, you'll see that the ramdisk is
copied to the wrong place; see my above note about the recent snapshot
patch.
Also, the default serial console configuration for Assabet is to run at
9600bps, whereas bootldr is built to run at 115200. This may be why you
don't see anything; check the value of CONFIG_SA1100_DEFAULT_BAUDRATE.
> I am also wondering which version of bootldr I should use. John
> Dorsey has a patch against Nov-26-2000 CVS bootldr. However, someone
> in this list claimed that it only works with NetBSD. Then Robert
> released a patch about two weeks to make bootldr working with Linux.
> This patch has been merged into the CVS tree. Now, John Dorsey
> released a newest patch for BIG_KERNEL support (isn't it supported
> already?) and solving static memory configuration problem. So what
> kind of combination should I use now? Really confused.
I've never tried it with BSD, but I'm reasonably hopeful that it will
work with Linux.
Also note that I haven't done anything with BIG_KERNEL, and don't use it
myself; it's just an adjustment of the partition maps to allow a larger
kernel to be flashed.
Basically, if you think you can live with a ramdisk for the time being,
I'd recommend the newest patch to the current CVS tree. (This way you
get all the Compaq goodies like command line history, as well as working
SA-1111 support.) If you have a phase 5 Assabet, see my note from
yesterday about the bank zero timings.
If getting up and running with JFFS (version 1) is more important, then
use the 26-November patch/binary, but note that the SA-1111 will be
flaky.
This should all be resolved within a week or so, when I finally get time
to work on bootldr instead of hardware bringup.
Good luck!
-jd
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