From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail1.bemta12.messagelabs.com ([216.82.251.2]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YZpbR-0001QX-6C for linux-mtd@lists.infradead.org; Sun, 22 Mar 2015 23:48:21 +0000 From: Iwo Mergler To: Boris Brezillon Date: Mon, 23 Mar 2015 10:45:33 +1100 Subject: RE: RFC: detect and manage power cut on MLC NAND Message-ID: References: <0D23F1ECC880A74392D56535BCADD7354973E51A@NTXBOIMBX03.micron.com> <55093B1E.2050805@dave.eu> <0D23F1ECC880A74392D56535BCADD7354973E995@NTXBOIMBX03.micron.com> <550A8D19.90404@dave.eu> <20150319101246.26806e95@bbrezillon> , <20150320092611.2648f3d5@bbrezillon> In-Reply-To: <20150320092611.2648f3d5@bbrezillon> Content-Language: en-AU Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "Jeff Lauruhn \(jlauruhn\)" , "dedekind1@gmail.com" , Richard Weinberger , Andrea Scian , "linux-mtd@lists.infradead.org" , Andrea Marson List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 20 Mar 2015 19:26:11 +1100 Boris Brezillon wrote: > I've read many times that MLC pages should be programmed in ascending > order (0, 1, 2, 3, ..., N), and if you take a look at MLC datasheet > you'll see that paired pages are not contiguous (here is an example > [1], page 55-56 describe how pages are paired together). >=20 > My question is: is there a reason for interleaving paired pages with > other pages (write disturbance mitigation ?) ? >=20 > If there is no specific reason but to annoy software developers :-), I don't know for sure, but it seems that groups of pages are sharing some resources. For instance, I've seen a few bit error patterns which looked like this (256MB SLC, pages in one block): -------------------------------X-X-X-X-X-X-X-X-X-X-X-X-X-X-X-X-X The pages marked with 'X' have a single bit error at the same bit offset in every page. That is, even on a SLC device, there is some sort of page interleaving pattern at work. In this case, maybe they share a broken sense amplifier or similar. I currently think that the rule about the ascending order is a generalisation for unknown NAND architecture. In my example, it may well be slightly better to write (0,2,4,6,8,10,12,14,1,3,5, 7,9,11,13,15,16,18,20,22,24,26,28,30,17,19,21,23,25,27,29,31). Unless someone tells me otherwise, I guess that the paired pages probably should be written in sequence anyway (0,4,1,5,etc). Some of the backup methods appear suggestive of this. Best regards, Iwo