linux-kernel - Re: [PATCH 0/4] mtd: add support for pairing scheme description

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Date:	Fri, 10 Jun 2016 19:16:25 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Richard Weinberger <richard@....at>, linux-mtd@...ts.infradead.org,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] mtd: add support for pairing scheme description

Hi Boris,

I've mostly just reviewed the cover and first patch for now, since that
sets up the rest. A few questions and comments. I hope to review some
more and have more to say later this weekend.

On Mon, Apr 25, 2016 at 12:01:17PM +0200, Boris Brezillon wrote:
> Hi,
> 
> This series is the first step towards reliable MLC/TLC NAND support.
> Those patches allows the NAND layer to expose page pairing information
> to MTD users.

Have you surveyed many types of NAND to get a representative sampling of
what kind of pairing schemes are out there? Do you think you've covered
the possibilities well enough in your API? I have a few comments on the
patches to this effect. I honestly don't know the answer to these
questions, because AFAIR, this is rarely well documented in datasheets.

> The plan is to teach UBI about those constraints and let UBI code take
> the appropriate precautions when dealing with those multi-level cells
> NANDs. The way we'll handle this "paired pages" constraint will be
> described soon in a series adapting the UBI layer, so stay tune ;).
> 
> Note that this implementation only allows page pairing scheme description
> when the NAND has a full-id entry in the nand_ids table.
> This should be addressed in some way for ONFI and JEDEC NANDs, though
> I'm not sure how to handle this yet.

Do ONFI or JEDEC parameter pages even provide this kind of info? The
ONFI spec doesn't mention paired pages.

Brian

> Best Regards,
> 
> Boris
> 
> Boris Brezillon (4):
>   mtd: introduce the mtd_pairing_scheme concept
>   mtd: nand: implement two pairing scheme
>   mtd: nand: add a pairing field to nand_flash_dev
>   mtd: nand: H27UCG8T2ATR: point to the correct pairing scheme
>     implementation
> 
>  drivers/mtd/mtdcore.c        | 62 ++++++++++++++++++++++++++++
>  drivers/mtd/mtdpart.c        |  1 +
>  drivers/mtd/nand/nand_base.c | 97 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/mtd/nand/nand_ids.c  |  2 +-
>  include/linux/mtd/mtd.h      | 64 +++++++++++++++++++++++++++++
>  include/linux/mtd/nand.h     |  5 +++
>  6 files changed, 230 insertions(+), 1 deletion(-)
> 
> -- 
> 2.7.4
>