Re: [EXT] Re: [PATCH RFC] mtd: rawnand: Cure MICRON NAND partial erase issue

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Bean,

"Bean Huo (beanhuo)" <beanhuo@micron.com> wrote on Fri, 7 Dec 2018
13:12:56 +0000:

> >+Bean,
> >
> >Hi Thomas,
> >
> >First of all, I'd like to thank you for sharing this patch. I'm pretty sure this will
> >save days of painful debug sessions to a lot of people.
> >
> >On Thu, 29 Nov 2018 22:12:50 +0100 (CET) Thomas Gleixner
> ><tglx@linutronix.de> wrote:
> >  
> >> On some Micron NAND chips block erase fails occasionaly despite the
> >> chip claiming that it succeeded. The flash block seems to be not
> >> completely erased and subsequent usage of the block results in hard to
> >> decode and very subtle failures or corruption.
> >>
> >> The exact reason is unknown, but experimentation has shown that it is
> >> only happening when erasing an erase block which is partially written.
> >> Partially written erase blocks are not uncommon with UBI/UBIFS.  Note,
> >> that this does not always happen. It's a rare and random, but eventually  
> >fatal failure.  
> >>
> >> For now, just blindly write 6 pages to 0. Again experimentation has
> >> shown that it's not sufficient to write pages at the beginning of the
> >> erase block. There need to be pages written in the second half of the
> >> erase block as well. So write 3 pages before and past the middle of the block.
> >>
> >> Less than 6 pages might be sufficient, but it might even be necessary
> >> to write more pages to make sure that it's completely cured. Two pages
> >> still failed, but the 6 held up in a stress test scenario.
> >>
> >> This should be optimized by keeping track of writes, but that needs
> >> proper information about the issue.
> >>
> >> As it's just observation and experimentation based, it's probably wise
> >> to hold off on this until there is proper clarification about the root
> >> cause of the problem. The patch is for reference so others can avoid
> >> to decode this again, but there is no guarantee that it actually fixes
> >> the issue completely.  
> >
> >I agree. I Cc-ed Bean from Micron. Maybe he can provide more information
> >on this issue.
> >  
> >>
> >> Therefore:
> >>
> >> Not-yet-signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> >>
> >> Cc: Boris Brezillon <boris.brezillon@bootlin.com>
> >> Cc: Miquel Raynal <miquel.raynal@bootlin.com>
> >> Cc: Richard Weinberger <richard@nod.at>
> >>
> >> ---
> >>
> >> P.S.: This was debugged on an older kernel version (sigh) and ported
> >>       forward without actual testing on mainline. My MTD foo is a bit
> >>       rusty, so I won't be surprised if there are better ways to do that.  
> >
> >Let's first wait for Bean's feedback before discussing implementation details.
> >BTW, do you remember the part number(s) of the flash(es) impacted by this
> >problem in your case?
> >  
> Thanks, let me know this issue, I will look at this

I think it's time for you to comment on the situation.


Thanks,
Miquèl