From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu, 1 Oct 2015 17:07:43 +0200
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: David Woodhouse <dwmw2@infradead.org>, Brian Norris
 <computersforpeace@gmail.com>, linux-mtd@lists.infradead.org
Cc: Josh Wu <josh.wu@atmel.com>, Ezequiel Garcia
 <ezequiel.garcia@free-electrons.com>, Maxime Ripard
 <maxime.ripard@free-electrons.com>, Greg Kroah-Hartman
 <gregkh@linuxfoundation.org>, Huang Shijie <shijie.huang@intel.com>, Bryan
 Wu <bryan.wu@analog.com>, devel@driverdev.osuosl.org,
 linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: nand: pass page number to ecc->write_xxx() methods
Message-ID: <20151001170743.3aa0d6fa@bbrezillon>
In-Reply-To: <1440436219-31625-1-git-send-email-boris.brezillon@free-electrons.com>
References: <1440436219-31625-1-git-send-email-boris.brezillon@free-electrons.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
List-Id: Linux MTD discussion mailing list <linux-mtd.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/options/linux-mtd>,
 <mailto:linux-mtd-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/linux-mtd/>
List-Post: <mailto:linux-mtd@lists.infradead.org>
List-Help: <mailto:linux-mtd-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/linux-mtd>,
 <mailto:linux-mtd-request@lists.infradead.org?subject=subscribe>

Hi Brian,

On Mon, 24 Aug 2015 19:10:19 +0200
Boris Brezillon <boris.brezillon@free-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