linux-kernel - RE: [PATCH] mtd: fsl_elbc_nand: set NAND_NO_SUBPAGE

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Date:	Tue, 6 May 2014 09:57:48 +0000
From:	"Gupta, Pekon" <pekon@...com>
To:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"Paul Gortmaker" <paul.gortmaker@...driver.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Prabhakar Kushwaha <prabhakar@...escale.com>
CC:	"lugovskoy@....rtsoft.ru" <lugovskoy@....rtsoft.ru>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] mtd: fsl_elbc_nand: set NAND_NO_SUBPAGE_WRITE flag if
 using hardware ECC

Hi Nikita,

>From: Nikita Yushchenko
>
>Per MPC8572E manual, sec 14.4.3.1.3: "Transfers shorter than a full page,
>however, require software to prepare the appropriate ECC in the spare
>region"
>
>Need to set NAND_NO_SUBPAGE_WRITE flag. If this is not done, then
>generic nand_write_subpage_hwecc() is called instead of driver's
>write routine, which results into OOPS dereferencing NULL chip->ecc.hwctl
>pointer.
>
>Signed-off-by: Nikita Yushchenko <nyushchenko@....rtsoft.ru>
>---

This one is already solved.

Please refer below discussion and its previous thread on
why NAND_NO_SUBPAGE_WRITE should _not_ be set,
because it breaks compatibility with older UBIFS images.

http://lists.infradead.org/pipermail/linux-mtd/2014-April/053262.html

Also below is the appropriate fix without breaking backward compatibility.
http://lists.infradead.org/pipermail/linux-mtd/2014-May/053745.html


with regards, pekon
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