From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from protonic.xs4all.nl ([83.163.252.89]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Wzm3b-0002AW-Up for linux-mtd@lists.infradead.org; Wed, 25 Jun 2014 12:12:08 +0000 Date: Wed, 25 Jun 2014 14:11:33 +0200 From: David Jander To: "Gupta, Pekon" , "Brian Norris" Subject: Re: [FRC] [PATCH] MTD: nand_base.c: Enable support for Samsung E-die SLC NAND Message-ID: <20140625141133.247d62a3@archvile> In-Reply-To: <20980858CB6D3A4BAE95CA194937D5E73EAF7689@DBDE04.ent.ti.com> References: <1403259137-22171-1-git-send-email-david@protonic.nl> <20980858CB6D3A4BAE95CA194937D5E73EAF6A08@DBDE04.ent.ti.com> <20980858CB6D3A4BAE95CA194937D5E73EAF7560@DBDE04.ent.ti.com> <20140625133129.060cd535@archvile> <20980858CB6D3A4BAE95CA194937D5E73EAF7689@DBDE04.ent.ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Ted Juan , "sjhill@realitydiluted.com" , "tglx@linutronix.de" , "linux-mtd@lists.infradead.org" , David Woodhouse List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Dear Pekon, On Wed, 25 Jun 2014 11:55:26 +0000 "Gupta, Pekon" wrote: > Hi David, > > >From: David Jander [mailto:david.jander@protonic.nl] > >>"Gupta, Pekon" wrote: > >> >From: Ted Juan [mailto:ted.juan@gmail.com] > >> >Dear Pekon, > >> > > >> >I backup the raw data to data2[] before doing > >> >elm_decode_bch_error_page(); Dump code is as below. The raw data is the > >> >same with the correction data that all more than 8 bit-flips. > >> > > >> (a) In that case you should contact the Flash vendor here. > >> Fresh NAND device from factory should not violate the spec. > >> I don't suspect a driver issue here, because the raw data read itself > >> has random bit-flips. > > > >Sorry to interrupt, but this does sound serious. Are you absolutely sure > >your hardware is OK? Is the power-supply clean and well enough decoupled? > >Timings within specs? If electrical specifications are not met, this could > >explain the bit-flips. > > > I don't have the hardware (board), I'm just helping Ted as I'm actively > involved with OMAP NAND drivers from TI side. Ted is the original developer > working on this board. Ok. > However, I don't suspect this to be board supply or noise issue because: > (1) A timing mis-match would cause read-failure for whole word, > not just few bits in the word. Yes that would be the most probable effect of a timing issue. Just a few bit-flips in a word is unlikely (but not impossible!) to be caused by timing issues. > (2) Also, power-supply noise would not cause bit-flips in erased-page, > Because erase operation inside flash is usually driver by charged-pumps > so a dynamic supply noise may not cause random bit-flips. Though it can > can erase-failures, which will be detected on reading STATUS register. Please bear in mind that the erase can be successful for the first few (milli-)seconds. If the power supply was out of specs during erase, it is perfectly possible that a few random bits flip back to "programmed" state after a while. That would not be caught by the status check. > > It is possible that Samsung is at fault here (they screwed up the specs > > for this > >version anyway), but double checking the hardware looks like a good idea > >here... > > > Agree. But hardware issue will be difficult to identify and debug. > > Ted, > Plz relax timing by 10-20% and check if that makes a difference. That is a good idea to check, but I would also try to influence the power-supply or -decoupling to see if that is sensible variable. Do you have cold-spray? Try to use it and see if it affects the result. Best regards, P.S.: Anyone care to give comment on my patch? Not that you two effectively hijacked this thread for only slightly tangentially related issues... ;-) -- David Jander Protonic Holland.