From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp125.sbc.mail.sp1.yahoo.com ([69.147.65.184]) by bombadil.infradead.org with smtp (Exim 4.69 #1 (Red Hat Linux)) id 1M26rT-0000Xt-HM for linux-mtd@lists.infradead.org; Thu, 07 May 2009 16:54:26 +0000 From: David Brownell To: "vimal singh" Subject: Re: [PATCH 2/2] NAND on DM355: Add 4-bit ECC support for large page NAND chips Date: Thu, 7 May 2009 09:54:10 -0700 References: <46149.192.168.10.89.1241686786.squirrel@dbdmail.itg.ti.com> <41906.192.168.10.89.1241689856.squirrel@dbdmail.itg.ti.com> In-Reply-To: <41906.192.168.10.89.1241689856.squirrel@dbdmail.itg.ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200905070954.10987.david-b@pacbell.net> Cc: davinci-linux-open-source@linux.davincidsp.com, nsnehaprabha@ti.com, linux-mtd@lists.infradead.org, akpm@linux-foundation.org, dwmw2@infradead.org, tglx@linutronix.de List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thursday 07 May 2009, vimal singh wrote: > >> How about leaving bytes '4' and '5' for bad block marker, to support 16-bit > >> NAND parts too. > > > > This 4-bit ECC engine only works for 8-bit wide parts ... > > or are you suggesting that in case TI re-engineers that > > engine in the future? > > I am omap guy and was not aware of that. In omap HW BCH > ECC (4- or 8- bit correction)can work both kind of memories. I'm somewhat more of an OMAP guy too -- just got sucked in to trying to get a dm355 board to run off NAND in mainline-bound code, and you can see where that landed me! Last I looked at the OMAP2/OMAP3 NAND controller driver, it didn't yet support most fancy hardware features, like ECC using more than one bit or the prefetch/postwrite logic. One nice feature of that OMAP2/OMAP3 controller, beyond the support for 8 bit ECC, is that it buffers the ECC syndrome data so that it doesn't need NAND_ECC_HW_OOB_FIRST logic to prevent trashing the manufacturer OOB markers. The limit of max 4K pages seems like not a big worry for now. - Dave