From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eusmtp01.atmel.com ([212.144.249.242]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Y68fP-0001Rk-7c for linux-mtd@lists.infradead.org; Wed, 31 Dec 2014 02:05:44 +0000 Message-ID: <54A359AE.3080105@atmel.com> Date: Wed, 31 Dec 2014 10:04:30 +0800 From: Josh Wu MIME-Version: 1.0 To: Subject: Re: Does UBIFS NAND ECC info get stored in OOB? References: In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi, Steve On 12/31/2014 3:44 AM, Steve deRosier wrote: > Hi All, > > Sorry if this is a stupid question, but I found a number of old > archived messages that explicitly state that UBIFS (actually, probably > UBI) doesn't utilize the OOB of a NAND flash at all for storing the > ECC information. Could you list out these UBI/UBIFS messages so that people can help? > And as near as I can tell from behavior and code, it > does certainly store ECC info in the OOB area. > > So, does UBIFS utilize the OOB area to store ECC bits? And if not, > where/how does it store this information? > > I'm starting to assume that you're simply saying that UBIFS itself > doesn't use the OOB area, nor even handles the ECC itself, but that's > up to the chip driver layer. And that the driver will handle the ECC > and OOB as appropriate. Am I correct? yes. I think you are correct. > > Details of my question: > > We're having some trouble with filesystem corruption on a Linux 3.8 > kernel based on an Atmel SAM9g25 controller. The controller does have > the PMECC unit. Does your system can boot up correctly and work sometime? or you cannot mount your UBI filesystem at all? Could get me a system boot log about your corruption, and another boot log without corruption? > > It utilizes the mtd/nand/atmel_nand.c driver. This driver has the > PMECC bits in it and does appear to write/read/correct-via ECC bits in > the OOB area of the NAND. > > We're using UBIFS for our rootfs. > > And yes, I understand the 3.8 kernel is old, and we're upgrading, but > I'm trying to figure out why we're having the problems as I'm assuming > it's not a bug in the code but more of a configuration or process or > hardware issu So could give me some configuration about your PMECC? 4 bits correction in 512 bytes or else? What is your nand flash ecc minimal requirement? Best Regards, Josh Wu > > One example of finding that UBI & UBIFS doesn't use the OOB area is " > this is not a problem for UBI/UBIFS, because neither UBIFS nor UBI use > OOB area;" from http://www.linux-mtd.infradead.org/doc/ubifs.html > > Thanks any help, > - Steve > > ______________________________________________________ > Linux MTD discussion mailing list > http://lists.infradead.org/mailman/listinfo/linux-mtd/