Some questions on bit-flips and JFFS2

[Ricard Wanderlof]

On Tue, 11 May 2010, Thorsten Mühlfelder wrote:

>> I think in this case the partition in question just held a raw Linux
>> kernel with no file system, so JFFS2 is out of the picture here.
>>
> But unfortunately the Sam-Ba 2.5 tool has a bug: it uses different bad block
> table structure and Linux refuses to read/write every block, that was written
> by Sam-Ba 2.5 because it recognizes them as bad blocks.
> So for now I have no idea what I can do to reduce the failing rate.

I don't know if this is a good way, but you could patch your kernel so it 
doesn't stop you from erasing/writing badblocks. Then you could write your 
own application which checks for bad blocks in the same way that the 
Sam-Ba 2.5 tool does, which would allow you to rewrite everything written 
by that tool.

> At least there is still no board using Samsung flash that has failed and I
> hope all problems are related to the Micron flash.

Even if you are not using jffs2, mtd will still perform single-bit error 
correction thanks the the ECC algorithm, so you need to be unlucky enough 
and get two bitflips within a 256 byte region for the system to fail.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30