From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-out.m-online.net ([212.18.0.9]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1d41Ow-00049x-SI for linux-mtd@lists.infradead.org; Fri, 28 Apr 2017 08:37:21 +0000 Date: Fri, 28 Apr 2017 10:36:52 +0200 From: Lukasz Majewski To: Andrea Adami Cc: Ricard Wanderlof , linux-mtd@lists.infradead.org Subject: Re: Problem with NAND memory data retention Message-ID: <20170428103652.62990916@jawa> In-Reply-To: References: <20170427122502.285d16ba@jawa> <20170427150416.2c6bba07@jawa> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Andrea, Thanks for your response! > On Thu, Apr 27, 2017 at 3:04 PM, Lukasz Majewski > wrote: >=20 > > Hi Ricard, > > > > > > > > On Thu, 27 Apr 2017, Lukasz Majewski wrote: > > > > > > > I'd like to ask you for sharing your experience with NAND Flash > > > > devices > > > > - which may be older that their data retention time. > > > > > > > > I've a problem with Flash NAND memory (Samsung 128Mx8). > > > > > > > > In the data sheet [1] the manufacturer claims that it has 10 > > > > years for data retention. The device equipped with it is a bit > > > > older than 10 years. > > > > > > > > > > > > How one can diagnose that data retention time for NAND Flash has > > > > been exceeded? > > > > > > > > Is that: > > > > > > > > - The number of bit flip errors on a RW page so large that ECC > > > > cannot fix it? > > > > > > > > - Or are whole RW pages erased (0xFF)/corrupted/cleared (0x00)? > > > > > > > > - Or any other evidence? > > > > > > > > Thanks in advance for your help. > > > > > > I think the interpretation is that the manufacturer guarantees > > > that under the circumstances specified (temperature, supply > > > voltage, erase cycles etc) that the data will be retained for at > > > least ten years, beyond that it's just not specified. It doesn't > > > mean that something catastrophic will happen after ten years, > > > i.e. ten years is not a hard limit beyond which things start > > > going haywire. > > > > Thanks for your explanation. > > > > > > > > I can't say I have experience with old NAND flashes loosing their > > > data, but technically I would expect that what happens is that > > > eventually the charge leaks away from the bit cells, causing bit > > > flips, quite simply, so it's the same mechanism that requires the > > > flash to be 'scrubbed' periodically to check if the data needs to > > > be rewritten. > > > > > > I.e. it's the first case in your list, the number of bit flips > > > increases. > > > > Unfortunately with my device I do experience the second scenario. > > > > I do observe pages read as zeros. > > >=20 > Hello, >=20 > I think I have seen the same issue: one defective device did not > respond to CFI QRY. >=20 > http://lists.infradead.org/pipermail/linux-mtd/2014-May/053872.html I do not have (yet) the CFI commands dump, but in my case Erase-> Reflash sequence causes the file content to be correct. IMHO, If the Flash memory controller itself is broken, then "re-flashing" would not help. Maybe - in my case the NAND flash driver (2.6 kernel) causes the issue (with zero filled page showing up in the middle of a YAFFS file) by some write done at mistakingly calculated address? Any ideas/hints are more than welcome :-) Best regards, =C5=81ukasz Majewski >=20 > These devices were sold in 2002-2003 so they are now >15yrs old and I > have two of them working flawlessy. >=20 > Regards > Andrea >=20 >=20 >=20 >=20 > > > > For example in the middle of a file - page sized (2K) data is read > > as zero. And this file is RO (no modification). And such zero read > > is persistent - happens all the time. The only way is to replace > > the whole file (erase it and write again). > > > > We use yaffs file system. > > > > And such errors pop up in random places. > > > > > > > > The fewer erase cycles that a given flash block has seen, the less > > > wear there has been on the insulation, and the better the > > > retention would be. The ten year spec is under the worst case > > > condition of the maximum number of erase cycles having been > > > performed on the flash. > > > > > > /Ricard > > > > > > > > > > Best regards, > > > > Lukasz Majewski > > > > -- > > > > DENX Software Engineering GmbH, Managing Director: Wolfgang > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, > > Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: > > wd@denx.de > > > > ______________________________________________________ > > Linux MTD discussion mailing list > > http://lists.infradead.org/mailman/listinfo/linux-mtd/ > > Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de