Re: [Openpxa-users] PXA310: double bit errors on NAND

[pieterg <pieterg@gmx.com>]

On Monday, November 08, 2010 15:54:43 Bjørn Forsman wrote:
> I get "double bit error @ page" messages while working with NAND on a
> Colibri PXA310 module. Basically, when I write an UBI image to NAND,
> either with U-Boot "nand write" or "nandwrite" from mtd-utils,
> everything is OK on the *first* mount. But on the second mount I get
> several "double bit error @ page" messages and mount fails.

You are not erase-block padding your image, when you write it?
That's the mistake I made (with jffs2 in my case), in that openpxa-users
thread you mention.
As soon as I found out my image was eraseblock padded, and fixed that,
the number of single/double bit errors was reduced dramatically, 
but some errors remained.

I haven't yet had the time to further investigate this, my preliminary 
conclusion is that the Samsung K9K's, though advertised as SLC, 
are very poor quality, and they probably need a better ecc than 
Hamming (as the pxa nand controller implements).
And also that jffs2 seems to care less than ubi(fs) when double bit errors 
do happen.(ubifs often refused to even mount when biterrors occurred, 
jffs2 so far always continued with what remained)
That's the reason why I'm using jffs2 for the time being, a non-booting 
device is worse than a device with a corrupted file.
(from a theoretical point of view however both are equally bad of course, 
this issue does need to be resolved)

Rgds, Pieter