Some questions on bit-flips and JFFS2

[Thorsten Mühlfelder]

Am Tuesday 11 May 2010 16:55:19 schrieb Norbert van Bolhuis:
> Or can you put a kernel image on it beforehand ? are we talking about
> deployed systems or to be deployed systems ?

Of course the thoughts about UBIFS are only for future systems, that are not 
deployed yet. Also there is a newer version of the Atmel Sam-ba tool, that 
fixes the bad blocks problem.
But because of the Sam-ba problem it seems to be hard to get a fix done for 
already deployed systems.

> Anyway, if you switch to UBIFS and *can* put the kernel image on UBIFS
> fatal bit flips in the uImage on bare NAND don't matter.
> On the other hand: fatal bit flips in bootstrap/u-boot/u-boot_env will
> still prevent the system to boot. So maybe also refreshing those images is
> necessary.

This is right. But as long as the kernel Image is about 1.5 MB and all the 
U-Boot stuff is only about 300 kB it would still increase the security. 
Furthermore UBIFS will have other advantages (e.g. lower mount times), too.

> You need a recent linux kernel and u-boot for them to support UBIFS.
>
> Note that: if you would upgrade your system with a new u-boot/linux and
> UBIFS i.s.o. JFFS2, *everything* on flash will change. If you want to do
> this for deployed systems you need a huge upgrade script.

This won't be done for deployed systems ;-)

> I don't use NAND+UBIFS myself, so I have no experience there.
>
> The below pointers should have some relevant info though:
>
> - u-boot home-page: http://www.denx.de/wiki/U-Boot/WebHome
> - u-boot mailing list: http://lists.denx.de/pipermail/u-boot/
> - u-boot source code GIT tree:
> http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=tree (checkout boards
> with NAND and boot-from-NAND support)
> - specialized GIT trees for NAND and UBI:
> http://www.denx.de/wiki/U-Boot/Custodians

Thanks, will have to take a look at it later. But for now it's a higher 
priority to reduce failure rate in already deployed systems.

Regards
Thorsten