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Date: Mon, 29 Aug 2016 13:38:47 -0700
From: Brian Norris <computersforpeace@gmail.com>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Karl Beldan <kbeldan@baylibre.com>, linux-mtd@lists.infradead.org,
 linux-kernel@vger.kernel.org, Richard Weinberger <richard@nod.at>,
 David Woodhouse <dwmw2@infradead.org>, Sekhar Nori <nsekhar@ti.com>,
 Kevin Hilman <khilman@baylibre.com>,
 Karl Beldan <karl.beldan+oss@gmail.com>
Subject: Re: [PATCH] mtd: nand: davinci: Reinitialize the HW ECC engine in
 4bit hwctl
Message-ID: <20160829203847.GA102453@google.com>
References: <20160829074550.29247-1-kbeldan@baylibre.com>
 <20160829115930.517a133e@bbrezillon>
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On Mon, Aug 29, 2016 at 11:59:30AM +0200, Boris Brezillon wrote:
> On Mon, 29 Aug 2016 07:45:49 +0000
> Karl Beldan <kbeldan@baylibre.com> wrote:
> 
> > This fixes subpage writes when using 4-bit HW ECC.
> > 
> > There has been numerous reports about ECC errors with devices using this
> > driver for a while.  Also the 4-bit ECC has been reported as broken with
> > subpages in [1] and with 16 bits NANDs in the driver and in mach* board
> > files both in mainline and in the vendor BSPs.
> > 
> > What I saw with 4-bit ECC on a 16bits NAND (on an LCDK) which got me to
> > try reinitializing the ECC engine:
> > - R/W on whole pages properly generates/checks RS code
> > - try writing the 1st subpage only of a blank page, the subpage is well
> >   written and the RS code properly generated, re-reading the same page
> >   the HW detects some ECC error, reading the same page again no ECC
> >   error is detected
> > 
> > Note that the ECC engine is already reinitialized in the 1-bit case.
> > 
> > Tested on my LCDK with UBI+UBIFS using subpages.
> > This could potentially get rid of the issue workarounded in [1].
> > 
> > [1] 28c015a9daab ("mtd: davinci-nand: disable subpage write for keystone-nand")
> > 
> > Signed-off-by: Karl Beldan <kbeldan@baylibre.com>
> 
> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> 
> Brian, can you take this patch directly in your tree. If that's not
> possible, let me know, I'll add the Fixes and Cc:stable tags and take
> it for 4.9.

Would this be correct?

Fixes: 6a4123e581b3 ("mtd: nand: davinci_nand, 4-bit ECC for smallpage")

Brian