linux-kernel - Re: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip

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Message-ID: <1324132520.4240.26.camel@sauron.fi.intel.com>
Date:	Sat, 17 Dec 2011 16:35:20 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Scott Wood <scottwood@...escale.com>
Cc:	shuo.liu@...escale.com, dwmw2@...radead.org,
	Artem.Bityutskiy@...ia.com, linux-mtd@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, leoli@...escale.com
Subject: Re: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support
 large-page Nand chip

On Mon, 2011-12-12 at 15:30 -0600, Scott Wood wrote:
> On 12/12/2011 03:19 PM, Artem Bityutskiy wrote:
> > On Mon, 2011-12-12 at 15:15 -0600, Scott Wood wrote:
> >> NAND chips come from the factory with bad blocks marked at a certain
> >> offset into each page.  This offset is normally in the OOB area, but
> >> since we change the layout from "4k data, 128 byte oob" to "2k data, 64
> >> byte oob, 2k data, 64 byte oob" the marker is no longer in the oob.  On
> >> first use we need to migrate the markers so that they are still in the oob.
> > 
> > Ah, I see, thanks. Are you planning to implement in-kernel migration or
> > use a user-space tool?
> 
> That's the kind of answer I was hoping to get from Shuo. :-)
> 
> Most likely is a firmware-based tool, but I'd like there to be some way
> for the tool to mark that this has happened, so that the Linux driver
> can refuse to do non-raw accesses to a chip that isn't marked as having
> been migrated (or at least yell loudly in the log).
> 
> Speaking of raw accesses, these are currently broken in the eLBC
> driver... we need some way for the generic layer to tell us what kind of
> access it is before the transaction starts, not once it wants to read
> out the buffer (unless we add more hacks to delay the start of a read
> transaction until first buffer access...).  We'd be better off with a
> high-level "read page/write page" function that does the whole thing
> (not just buffer access, but command issuance as well).

It looks like currently you can re-define chip->read_page, so I guess
you should rework MTD and make chip->write_page re-definable?

-- 
Best Regards,
Artem Bityutskiy

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