Re: [PATCH 0/9] drivers:mtd:UBI: add bakvol module for MLC NAND paired page issue

[Boris Brezillon <boris.brezillon@free-electrons.com>]

Hi Bean,

Next time you send a patch series, could send all the patches in reply
to the cover letter?

On Mon, 28 Sep 2015 07:02:35 +0000
Bean Huo 霍斌斌 (beanhuo) <beanhuo@micron.com> wrote:

> Hello,
> 
> This series aims at adding a bakvol module for MLC NAND paired page
> Power loss protection.
> MLC NAND paired page power loss is a known issue so far, MLC NAND pages are
> coupled in a sense that if you cut power while writing to a page, you corrupt not only
> this page, but also one of the previous pages which is paired with the current one.
> Currently, there is no a perfect solution for this. 
> This paired page solution is based on NAND multiple plane program feature. For this
> Patch, only used dual plane page program, means two different plane pages can
> Be programmed together at the same time.
> Dual plane page program only implements in backup operation. Only lower page data
> Be duplicated and back up into a internal log volume by dual plane program method.

Hm, I'm not very fond of the idea, especially because of the complexity
caused by dual plane program operations (you can't take a random block
to write your backup on it, which means WL is complexified too), and
the fact that you're duplicating data (thus introducing a performance
penalty and storage overhead).

> 
> This patch has been testing on Micron 70s/80s/90s MLC NAND.
> Of course there are some places needed to be improved and simplified.
> 
> Any suggestion and comments welcomed.

Sure, I'll try to review it soon.

Thanks for submitting those patches.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com