From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-gw0-f49.google.com ([74.125.83.49]) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QvSBX-0003iK-8L for linux-mtd@lists.infradead.org; Mon, 22 Aug 2011 10:56:52 +0000 Received: by gwb1 with SMTP id 1so3658539gwb.36 for ; Mon, 22 Aug 2011 03:56:47 -0700 (PDT) Subject: Re: [PATCH v3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip From: Artem Bityutskiy To: Scott Wood Date: Mon, 22 Aug 2011 13:58:33 +0300 In-Reply-To: <4E4EA70B.9050203@freescale.com> References: <1313634783-8855-1-git-send-email-b35362@freescale.com> <4E4D452C.7050805@parrot.com> <4E4DD661.5080006@freescale.com> <4E4E2571.20409@parrot.com> <4E4EA70B.9050203@freescale.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Message-ID: <1314010719.2644.114.camel@sauron> Mime-Version: 1.0 Cc: "linuxppc-dev@ozlabs.org" , "linux-mtd@lists.infradead.org" , LiuShuo , "dwmw2@infradead.org" , Matthieu CASTET Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2011-08-19 at 13:10 -0500, Scott Wood wrote: > On 08/19/2011 03:57 AM, Matthieu CASTET wrote: > > LiuShuo a écrit : > >> 于 2011年08月19日 01:00, Matthieu CASTET 写道: > >>> b35362@freescale.com a écrit : > >>>> From: Liu Shuo > >>>> > >>>> Freescale FCM controller has a 2K size limitation of buffer RAM. In order > >>>> to support the Nand flash chip whose page size is larger than 2K bytes, > >>>> we divide a page into multi-2K pages for MTD layer driver. In that case, > >>>> we force to set the page size to 2K bytes. We convert the page address of > >>>> MTD layer driver to a real page address in flash chips and a column index > >>>> in fsl_elbc driver. We can issue any column address by UA instruction of > >>>> elbc controller. > >>>> > >>> Why do you need to do that ? > >>> > >>> When mtd send you a 4k page, why can't you write it by 2*2k pages write ? > >> 1. It's easy to implement. > >> 2. We don't need to move the data in buffer more times, because we > >> want to use the HW_ECC. > >> > >> In flash chip per Page: > >> ---------------------------------------------------------------- > >> | first data | first oob | second data | second oob | > >> ---------------------------------------------------------------- > > How the bad block marker are handled with this remapping ? > > It has to be migrated prior to first use (this needs to be documented, > and ideally a U-Boot command provided do do this), or else special > handling would be needed when building the BBT. The only way around > this would be to do ECC in software, and do the buffering needed to let > MTD treat it as a 4K chip. It really feels like a special hack which would better not go to mainline - am I the only one with such feeling? If yes, probably I am wrong... -- Best Regards, Artem Bityutskiy