Testing a device using mtd_stresstest

[David Peverley]

Hi Artem,

Many thanks for the response ;

> MTD code is currently broken and CONFIG_MTD_NAND_VERIFY_WRITE causes
> errors when sub-pages are used. You should either disable this
> configuration option or fix MTD. We have this in our FAQ:
>
> http://www.linux-mtd.infradead.org/faq/ubi.html#L_subpage_verify_fail
I'm not sure what the implication of this is ; I understand that this
will cause the subpage test to fail with CONFIG_MTD_NAND_VERIFY_WRITE
enabled. However, the FAQ I had discounted as we use YAFFS2 and not
UBIFS. Given that should I still disable the write verify? At the
moment I'm inclined to leave it enabled as it seems to be regularly
catching failures that should not occur, such as the stress-test
failures noted.

We've also noticed that every so often we see "uncorrectable error:"
messages from nand_ecc.c - do you have any suggestions as to where to
start investigating here? So far I can't find a pattern to occurrences
or a regular way to reproduce.

Thanks again!

~Pev

On 6 February 2011 14:24, Artem Bityutskiy <dedekind1 at gmail.com> wrote:
> Hi,
>
> On Mon, 2011-01-31 at 12:12 +0000, David Peverley wrote:
>> Question 1 : The  mtd_subpagetest (which I suspect should fail as the
>> device doesn't support sub-pages). I googled around and found a
>> reference that maybe I should add NAND_NO_SUBPAGE_WRITE to the
>> options. I tried this and it made no difference. Out of curiosity I
>> grepped through drivers/mtd and found that *no* drivers actully use
>> this bit anyway...! Is it reasonable to ignore this or ought I address
>> it? Should I set the flag and expect it to have an effect?
>
> MTD code is currently broken and CONFIG_MTD_NAND_VERIFY_WRITE causes
> errors when sub-pages are used. You should either disable this
> configuration option or fix MTD. We have this in our FAQ:
>
> http://www.linux-mtd.infradead.org/faq/ubi.html#L_subpage_verify_fail
>
>
>> Question 2 : The mtd_stresstest test fails after anywhere between 1000
>> and 200,000 operations. I'm certain this is a Bad Sign. It fails in
>> nand_base.c:nand_write_page() in the verification step enabled by
>> MTD_NAND_VERIFY_WRITE. When I tested this on our previous board (that
>> ostensibly works fine) it failed the stress test after 2.6M operations
>> instead. Should I be expecting to never see a failure of the stress
>> test or is an occasional verify failure reasonably expected?
>
> Yes, the test is expected to never fail. You should try to dig and
> understand why is it failing and what is the reason.
>
> --
> Best Regards,
> Artem Bityutskiy (Артём Битюцкий)
>
>