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

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Message-ID: <20151001170743.3aa0d6fa@bbrezillon>
Date:	Thu, 1 Oct 2015 17:07:43 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org
Cc:	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

Hi Brian,

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

Best Regards,

Boris

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