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Subject: Re: Some questions on bit-flips and JFFS2
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Ricard Wanderlof <ricard.wanderlof@axis.com>
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Date: Wed, 05 May 2010 11:51:20 +0300
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On Wed, 2010-05-05 at 10:40 +0200, Ricard Wanderlof wrote:
> On Wed, 5 May 2010, Norbert van Bolhuis wrote:
> 
> >> I've already thought about something like this:
> >> 1. After first succesful bootup dump a mtd0 image and calculate a md5sum of
> >> it:
> >> nanddump -o -b -f mtd0.img /dev/mtd0
> >> 2. Before each shutdown dump the image again and check if the md5sum has
> >> changed.
> >> 3. If it has changed write the initial dump back:
> >> flash_eraseall /dev/mtd0
> >> nandwrite -p /dev/mtd0 mtd0.img
> >>
> >> Would this be the right method?
> >
> > yes that's the idea, given that "refreshing" really helps to prevent
> > (actually delay) future read disturbs.
> > ...
> >
> > Another problem is a sudden reboot (e.g. crash or power-loss). There's 
> > no check then.
> 
> Also, if a power failure occurs during erase or nandwrite the system will 
> not boot next time.

Unless you supply your device with an UPS :-)

I did not really follow the discussion, so sorry if the following is
unrelated: I think it should not be too difficult to teach JFFS2 to
force GC on eraseblocks with bit-flips.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)