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Subject: Re: [PATCH RFC] mtd: rawnand: Cure MICRON NAND partial erase issue
To: Richard Weinberger <richard@nod.at>
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From: Piotr Wojtaszczyk <wojtaszczykp@cumminsallison.com>
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Date: Mon, 3 Dec 2018 13:28:55 -0600
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On 12/3/18 1:02 PM, Richard Weinberger wrote:
> Am Montag, 3. Dezember 2018, 19:55:46 CET schrieb Piotr Wojtaszczyk:
>> On Thu, 29 Nov 2018 22:12:50 +0100 (CET)
>> Thomas Gleixner <tglx at 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.
>>
>> Doesn't UBI check block after erase in do_sync_erase()? Do the bitflips
>> develop over time?
> You mean ubi_self_check_all_ff()? This is a very expensive self-check
> which is disabled by default and makes only sense then you test UBI itself.
> Also think of power-cuts, what happens if you face power-loss right
> after mtd_erase() and before the check?
>
> Finally, I'm not sure if you can detect partial erase right after
> mtd_erase(). I fear failure happens after you write to that block.
>
> Thanks,
> //richard
>
>
Oh yes the ubi_self_check_all_ff() is indeed disabled. Partially erased 
blocks I think are being caught at attach in scan_peb(), they are put in 
ai->erase list for later erase again.

--

Peter