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From: Richard Weinberger <richard@nod.at>
To: Piotr Wojtaszczyk <wojtaszczykp@cumminsallison.com>
Cc: tglx@linutronix.de, linux-mtd@lists.infradead.org,
 boris.brezillon@bootlin.com, miquel.raynal@bootlin.com, beanhuo@micron.com
Subject: Re: [PATCH RFC] mtd: rawnand: Cure MICRON NAND partial erase issue
Date: Mon, 03 Dec 2018 20:02:16 +0100
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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