From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.nokia.com ([147.243.1.48] helo=mgw-sa02.nokia.com) by canuck.infradead.org with esmtps (Exim 4.72 #1 (Red Hat Linux)) id 1Q5e4G-0001CY-BQ for linux-mtd@lists.infradead.org; Fri, 01 Apr 2011 13:07:13 +0000 Subject: Re: [PATCH] Newly erased page read workaround From: Artem Bityutskiy To: Ivan Djelic In-Reply-To: <20110401121447.GA19151@parrot.com> References: <1301579475.2828.82.camel@localhost> <4D95708A.7080204@st.com> <1301640710.2789.11.camel@localhost> <4D958DC2.5000607@st.com> <1301647180.2789.35.camel@localhost> <4D9595AB.1050604@st.com> <20110401121447.GA19151@parrot.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 01 Apr 2011 16:04:41 +0300 Message-ID: <1301663081.2789.65.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Vipin Kumar , Viresh KUMAR , "linux-mtd@lists.infradead.org" , "David.Woodhouse@intel.com" Reply-To: Artem.Bityutskiy@nokia.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2011-04-01 at 14:14 +0200, Ivan Djelic wrote: > Did you consider this idea: if you have an unused byte available in oob, > program it to 0x00 when a page is programmed. I guess this depends on the the controller, but probably this could mean a substantial write overhead, not? > That way, you just need to check a single byte when you read a page in order > to distinguish erased pages from programmed pages. And by counting the number > of 1s in the byte, you can be robust to bitflips. Could you please explain some more what do you mean? So you write the 0x00 byte. Then when you read, you count the number of "1" bits in the byte. And what exactly this count gives you and to which bitflips you become robust? > As a special refinement, you could also "cleanup" pages detected as erased, in > order to iron out possible bitflips. What do you mean by "cleanup" a page? Thanks! -- Best Regards, Artem Bityutskiy (Артём Битюцкий)