linux-kernel - Re: [PATCH] mtd: nand: pass page number to ecc->write

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Date:	Thu, 1 Oct 2015 09:58:41 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org, Josh Wu <josh.wu@...el.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Huang Shijie <shijie.huang@...el.com>,
	Bryan Wu <bryan.wu@...log.com>, devel@...verdev.osuosl.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: nand: pass page number to ecc->write_xxx() methods

On Thu, Oct 01, 2015 at 05:07:43PM +0200, Boris Brezillon wrote:
> On Mon, 24 Aug 2015 19:10:19 +0200
> Boris Brezillon <boris.brezillon@...e-electrons.com> wrote:
> 
> > The ->read_xxx() methods are all passed the page number the NAND controller
> > is supposed to read, but ->write_xxx() do not have such a parameter.
> > 
> > This is a problem if we want to properly implement data
> > scrambling/randomization in order to mitigate MLC sensibility to repeated
> > pattern: to prevent bitflips in adjacent pages in the same block we need
> > to avoid repeating the same pattern at the same offset in those pages,
> > hence the randomizer/scrambler engine need to be passed the page value
> > in order to adapt its seed accordingly.
> > 
> > Moreover, adding the page parameter the ->write_xxx() methods add some
> > consistency to the current model.
> 
> Apparently nobody complained (or nobody cares :-)) about that patch,
> and I'll really need the page information if I want to support
> randomization/scrambling in the sunxi driver.
> 
> Do you have any objections to this patch

No, I guess not.

> (I can rebase it on mainline
> and check if new drivers have been added since the submission)?

I recently compile tested it against the tip of tree (don't know why I
didn't merge it then), but I think we added one driver since then. I
suppose a rebase is in order.

> I remember you pointed a trick you've used in the brcmnand driver to
> get this page information (storing it during the ->cmdfunc() or
> ->ctrl_cmd() call), but it would be way easier to have it directly in
> the ecc->write_xxx() parameters...

Right, that's not a pattern I'd really like people to copy...

Regards,
Brian
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