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

["Bean Huo (beanhuo)" <beanhuo@xxxxxxxxxx>]

>+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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
>>
>> Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
>> Cc: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
>> Cc: Richard Weinberger <richard@xxxxxx>
>>
>> ---
>>
>> 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

>Thanks,
>
>Boris
>

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