[U-Boot-Users] DiskOnChip, filesystems, and other booting options
wd at denx.de
Fri Apr 25 10:13:42 CEST 2003
in message <01qhav4dc6n97kctt8ob8f9qsjrva8v3sm at 4ax.com> you wrote:
> Yes, I know about these - what I meant was that the D.O.C support is
> still at
> the sector level, without any filesystem support.
IMHO all filesystem stuff for U-Boot should be split into a separate
layer (standalone applications acting as second stage bootstrap
> As far as I know (correct me if I'm wrong), NFTL does block-level
> remapping of
> bad blocks as well as wear levering by constantly changing the
> logical<>physical sector mapping on each write (so that if you write the
> "logical" sector 1000 times it would spread over all the flash).
So they claim to do.
> If my understanding is accurate, how can I use the U-Boot raw sectors
> disturbing the NFTL mapping that is handled by the Linux MTD package?
I think that the "binary partition" is not subject to this, i. e. you
can do direct I/O with the binary partition on the DoC.
> Besides, I've peeked into the D.O.C code in U-boot and it's full of NFTL
> references. In fact, as far as I can see, binary partitions are part of
> I've been looking at the files in fs/fdos/... and the CMD_FDC, CMD_FDOS
> which calls them., and I see it contains complete code to read a FAT
Something to be cleaned up and implemented in a more general way...
> I understand from the above that I don't need it, but just for the sake
> understanding - couldn't I drop the NFTL+normal filesystem and use JFFS2
> the raw D.O.C sectors, since JFFS2 does bad block mapping and wear
> (or does it??)
I don't know if it is possible to extend the size of the binary
partition to cover the whole device.
> OK, so where to I stand now?
> 1. My kernel correctly identifies the D.O.C but for some reason manages
> mount it only partially. /dev/mtdchar0 is non functional, but /dev/nftla
> to work between reboots. I can correctly partition the D.O.C using fdisk,
> the format is kept when I leave fdisk and re-run it, btu once I reboot,
> the partitioning done is lost.
That rings a bell to me. We fixed exactly such a problem once.
In the old version of the code some internal data structures of the
NFTL driver, which are initialized only at boot-time, become invalid
after you run nftl_format.
See my message "DOC / NFTL problem, and fix" from Aug 28, 2002, to
the MTD mailing list:
I don't know if they ever accepted the patch, and/or if it is
included with your version of the MTD tools. Just in case I attach
this patch again below.
> I think this part of my questions should be sent to the MTD list I guess.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
Do not underestimate the value of print statements for debugging.
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