linux-kernel - Re: [PATCH 1/3] mtd: nand: Add on-die ECC support

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Message-ID: <20150508212632.GA7167@bshelton-desktop>
Date:	Fri, 8 May 2015 16:26:32 -0500
From:	Ben Shelton <ben.shelton@...com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	punnaiah choudary kalluri <punnaia@...inx.com>,
	Richard Weinberger <richard@....at>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Punnaiah Choudary Kalluri 
	<punnaiah.choudary.kalluri@...inx.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: Re: [PATCH 1/3] mtd: nand: Add on-die ECC support

On 04/27, Brian Norris wrote:
> On Tue, Apr 28, 2015 at 08:18:12AM +0530, punnaiah choudary kalluri wrote:
> > On Tue, Apr 28, 2015 at 4:53 AM, Brian Norris
> > <computersforpeace@...il.com> wrote:
> > > On Tue, Apr 28, 2015 at 12:19:16AM +0200, Richard Weinberger wrote:
> > >> Oh, I thought every driver has to implement that function. ;-\
> > >
> > > Nope.
> > >
> > >> But you're right there is a corner case.
> > >
> > > And it's not the only one! Right now, there's no guarantee even that
> > > read_buf() returns raw data, unmodified by the SoC's controller. Plenty
> > > of drivers actually have HW-enabled ECC turned on by default, and so
> > > they override the chip->ecc.read_page() (and sometimes
> > > chip->ecc.read_page_raw() functions, if we're lucky) with something
> > > that pokes the appropriate hardware instead. I expect anything
> > > comprehensive here is probably going to have to utilize
> > > chip->ecc.read_page_raw(), at least if it's provided by the hardware
> > > driver.
> > 
> > Yes, overriding the chip->ecc.read_page_raw would solve this.
> 
> I'm actually suggesting that (in this patch set, for on-die ECC
> support), maybe we *shouldn't* override chip->ecc.read_page_raw() and
> leave that to be defined by the driver, and then on-die ECC support
> should be added in a way that just calls chip->ecc.read_page_raw(). This
> should work for any driver that already properly supports the raw
> callbacks.
> 

Hi Richard et al,

I'm guessing it's probably too late for the on-die ECC stuff to land in
4.2 at this point.  Is there anything I can do to help this along
(testing, etc.)?

Thanks,
Ben

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