From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [63.81.120.155] (helo=imap.sh.mvista.com) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1JeB4K-0005ej-IC for linux-mtd@lists.infradead.org; Tue, 25 Mar 2008 15:28:09 +0000 Message-ID: <47E91A5B.1060406@ru.mvista.com> Date: Tue, 25 Mar 2008 18:29:31 +0300 From: Sergei Shtylyov MIME-Version: 1.0 To: Laurent Pinchart Subject: Re: OF compatible MTD platform RAM driver ? References: <200803101606.39184.laurentp@cse-semaphore.com> <200803111139.12667.laurentp@cse-semaphore.com> <20080311224048.GA7642@localhost.localdomain> <200803251536.17795.laurentp@cse-semaphore.com> In-Reply-To: <200803251536.17795.laurentp@cse-semaphore.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: ben@simtec.co.uk, linuxppc-dev@ozlabs.org, linux-mtd@lists.infradead.org, David Gibson List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hello. Laurent Pinchart wrote: >>>>>here is the sram entry in our dts: >>>>Except that your implementation of it is not good. >>>>You're relying on the old obsolete flash binding with the "probe-type" >>>>field. The solution should be adapted to the new approach which uses >>>>values in the "compatible" field to indicate various sorts of flash >>>>device. >>>What "compatible" values should I use for ROM and RAM mappings ? >>That I'm not so sure of. We'll need to find some consensus. >>There may be existing IEEE1275 bindings for roms, which we should >>investigate. > Do you (or someone else here) have access to the IEEE1275 specification ? Is Yeah, and I can point you to it -- see the documantation section on http://www.openbios.org/... > there any ROM binding in there ? No. We initially called the flash devices that physmap_of driver controlled "rom" (I mean the "device_type" property) -- now this is obsoleted. >>Arguably RAM should be represented by a memory node, but >>that's going to get messy for this sort of application. Note that the OF "memory" type nodes do *not* represent RAM devices. > We're talking about a very specific type of RAM, used for permanent storage > with a battery backup. The RAM is really meant to be used as an MTD device > and as such I think it makes sense to describe it as an mtd-compatible device > on the local bus. > What about the following definition for the RAM node ? > nvram@2,0000 { Note that there's a OF "device_type" of "nvram", so your (generic) device name seems to add some mess. (IIRC, that OF device type didn't actually represent a "real" device, and only served to provide access to NVRAM for OF). > compatible = "mtd,ram"; The part before comma should be a company name or a stock ticker. What did you mean here? > reg = <2 0x0000 0x00100000>; > bank-width = <2>; > }; > Or should the node have a device-type property of either 'ram' or 'rom' with > the compatible property just referencing MTD ? The "device_type" properties are not required and their further creation has been discouraged on liunxppc-dev. > Best regards, WBR, Sergei