pxa3xx_nand issues

[pieterg]

On Saturday 25 September 2010 04:50:04 Haojian Zhuang wrote:
> On Thu, Sep 23, 2010 at 11:29 PM, pieterg <pieterg at gmx.com> wrote:
> > On Thursday 23 September 2010 13:32:26 pieterg wrote:
> >> On Thursday 23 September 2010 08:05:56 Eric Miao wrote:
> >> > On Thu, Sep 23, 2010 at 1:12 AM, pieterg <pieterg at gmx.com> wrote:
> >> > > In my search for the cause of the huge number of single/double bit
> >> > > errors I'm experiencing on colibri pxa320/310 devices, I've come
> >> > > across this commit
> >
> > http://git.kernel.org/?p=linux/kernel/git/ycmiao/pxa-linux-2.6.git;a=co
> >mmit;h=7f9938d0fd6c778bd0ce296a3e3b50266de2b892
> >
> >> > > According to the commitlog, it attempts to work around an issue
> >> > > regarding non-page-aligned reads.
> >> > > The workaround seems to force page-aligned access, by dropping the
> >> > > offset within the page (column address bytes).
> >> > > However, in my setup (with a jffs2 filesystem on nand),
> >> > > non-page-aligned reads never occur, but non-page-aligned writes
> >> > > occur very frequently. (during the jffs2 gc).
> >> > > These are also affected by this commit, while the commitlog does
> >> > > not state whether or not the same issue would occur for the
> >> > > program command, and in that case, whether or not the same
> >> > > workaround would apply.
> >> > >
> >> > > I've tried to revert the commit, but unfortunately this doesn't
> >> > > reduce the huge number of single/double bit errors (and jffs2 crc
> >> > > errors as a result) I'm getting.
> >> > >
> >> > > But having these non-aligned writes during GC, would that indicate
> >> > > a problem with my jffs2 image parameters perhaps?
> >> > > (though I cannot imagine this could actually cause double bit
> >> > > errors)
> >> >
> >> > It might not be related to the commit above.  The NAND controller
> >> > will always read the whole page and ignoring the column address,
> >> > that patch tries to make less confusion. The offset is actually
> >> > handled completely by software (memorized).
> >>
> >> I can see how the read offset works, but I do not quite see how this
> >> would work for writes (which call the same prepare_read_prog_cmd, and
> >> have their column address stripped as well).
> >> Found out that this happens when writing oob data by the way; these
> >> are writes with offset 2048 within the page. Jffs2 does this when
> >> writing cleanmarkers.
> >
> > Tested this, and found out that this commit is actually quite essential
> > for writes as well.
> > Without it, the OOB data doesn't get written.
> > So we can close this part of the topic, commit 7f9938d0 is perfectly
> > fine.
> >
> >> I could identify about 10 eraseblocks with pages which produce
> >> single/double bit errors.
> >> After I marked them bad (manually), I've seen no more bit errors, and
> >> the jffs2 rootfs has remained perfectly healthy.
> >
> > Turned out to be a short-term solution.
> > After a while I got more double-bit errors, and ended up bad-marking a
> > dozen or so other eraseblocks, and it does not seem to stop.
> >
> > Strangest thing is that when I write a new jffs2 image with uboot (nand
> > erase, nand write) or with the kernel (flash_eraseall, nandwrite), it
> > never contains any biterrors when I mount it.
> > Only after the filesystem has been mounted, gets modified, and then
> > after the first reboot, the biterrors are there.
>
> Could you make sure whether these "wrong" block are truely bad block?
> Maybe you can erase/write them continuously multi-times in XDB.

Unfortunately I don't have XDB.
However, I can erase/write/read them with u-boot and with the kernel 
(flash_eraseall / nandwrite), several times, without ever getting a 
NDSR_CS0_BBD status.
However, I get many NDSR_DBERR and NDSR_SBERR interrupts.

But because these occur during a read, the kernel never takes any action, 
the blocks will not be marked bad.
(And I find it hard to believe that such a huge number of blocks on a brand 
new chip would actually be bad)

Rgds, Pieter