[PATCH 1/2] mtd: OneNAND: Add runtime badblock check feature

[Kyungmin Park]

Hi,

> -----Original Message-----
> From: Artem Bityutskiy [mailto:dedekind1 at gmail.com]
> Sent: Sunday, June 13, 2010 6:27 PM
> To: Joonyoung Shim
> Cc: linux-mtd at lists.infradead.org; Kyungmin Park; Thomas Gleixner
> Subject: Re: [PATCH 1/2] mtd: OneNAND: Add runtime badblock check feature
> 
> On Tue, 2010-06-01 at 17:17 +0900, Joonyoung Shim wrote:
> > From: Kyungmin Park <kyungmin.park at samsung.com>
> >
> > This patch is to support runtime badblock checking. This supports only
> > OneNAND currently. The OneNAND badblock checking when boots occurs boot
> > time delay. We can reduce boot time because can detect badblock at
> > runtime.
> >
> > Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> 
> Hi, this feature is interesting. But why not to use bad block table
> instead of adding more complexity to the already very complex and
> difficult to follow code?

> 
> Also, if you really want this, it should be rather lazy checking, where
> you read OOB on demand, and then save this information to the in-ram
> BBT, and when you get another ->block_isbad() for a block which was
> previously checked, you do not read OOB for the second time.

It's based on BBT already. Now I set the BBT values as 0x2 and then check it at runtime and then mark it 0 for good, 3 for bad block.

Right, it's same word lazy checking and runtime check.

The original ideas are from UBI scan it read all blocks again at probe.
I just scan almost block read once at ubi scan.

Thank you,
Kyungmin Park

> 
> CCing Thomas, if we are lucky, he'll provide good input.
> 
> --
> Best Regards,
> Artem Bityutskiy (Артём Битюцкий)