Problems in Out of tree TI SDK omap2-nand driver (Re: [PATCH 3/3] nandtest: Introduce multiple reads & check iterations)

[Ezequiel Garcia]

I've changed the subject of this mail, since it seems we've moved from the
discussion.

On 05 May 10:58 AM, Gupta, Pekon wrote:
> 
> However, I know of some issues in OMAP NAND driver bundled with
> 3.2 kernel, which might be helpful in nailing down your specific issue.
> 

FWIW, I'm not using such driver anymore. Right after spotting this, we've
ran the *same* test on the mainline driver, which passed. This was the kick
we needed to start using mainline (we also need mainline for other reasons).

> (1) 3.2 kernel does not have concept of bitflip_threshold, so by default
> scrubbing and peb_torture happens even for single bit-flips. So please
> pull-in following patch series.
> [PATCH v2 0/7] mtd: Change meaning of -EUCLEAN return code on reads
> http://lists.infradead.org/pipermail/linux-mtd/2012-April/040945.html
> 

Isn't this series related to the higher-level treatment of bitflips?
In that case, it's not related to the issue I got. Keep in mind that
this simple test failed in our v3.2 stress (using this nandtest patch):

  * erase
  * write
  * read
  * read
  * ...
  * read (20 times)

> (2) OMAP NAND in 3.2 kernel does not factor bit-flips in empty pages
> Hence if empty pages with bit-flips are encountered, then it treats them
> like programmed pages and expects a ECC correction on them. But as
> empty pages do not have ECC stored in OOB, the driver bails out giving
> 'uncorrectable ecc' read errors.
> 

Since the test doesn't involve empty pages, I'd say this is not relevant.

If you're still interested in debugging the problematic TI SDK omap2-nand
driver, I suggest that you try using this nandtest patch and see how it
goes.

Despite you saying drivers can fail the test, I think it's still a nice test.
Keep in mind the nandtest tool reports the number of corrected ECC errors
after reads, so if that number is adding-up and increasing you can even
use this patch to see this evolution.

All in all, I think it's still a nice improvement on stock nandtest.
-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar