From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-gx0-f157.google.com (mail-gx0-f157.google.com [209.85.217.157]) by ozlabs.org (Postfix) with ESMTP id 62E25DDF55 for ; Wed, 25 Mar 2009 03:28:33 +1100 (EST) MIME-Version: 1.0 In-Reply-To: <200903241639.56637.sr@denx.de> References: <200903231151.10373.sr@denx.de> <200903241007.51321.sr@denx.de> <200903241639.56637.sr@denx.de> Date: Tue, 24 Mar 2009 10:28:31 -0600 Message-ID: Subject: Re: physmap_of and partitions (mtd concat support) From: Grant Likely To: Stefan Roese Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, devicetree-discuss list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Mar 24, 2009 at 9:39 AM, Stefan Roese wrote: > On Tuesday 24 March 2009, Grant Likely wrote: >> >> Sounds to me like a physmap_of driver bug. =A0I don't think there is = any >> >> advantage in changing the partition syntax since concatenated flash >> >> will always be used as a single device. =A0It doesn't make any sense = to >> >> try and span partitions over two nodes. >> > >> > Yes, I would really love to make this possible with only one flash nod= e. >> > But just think about the following system configuration: >> > >> > One Intel Strataflash (compatible =3D "cfi-flash") and one non-cfi >> > compatible flash (e.g. compatible =3D "jedec-flash"). And the user wan= ts to >> > define a partition that spans over both flash chips. How could this be >> > described in one flash node? >> > >> >> Do additional properties need to be added to describe the concat layo= ut? >> > >> > Not sure. If we have multiple identical devices they can currently be >> > described in one flash node. So with some changes to the physmap_of >> > driver this configuration will work with concat as well. But more comp= lex >> > is a system configuration as described above. Meaning two or more >> > non-identical chips. I don't see how this could be described in a sane >> > way in one flash node. >> >> Are there any such platforms? > > Yes, I know some. Even though they are currently not used with a partitio= n > spanning over those multiple chips (jedec and cfi). OK >> Is there much likelihood that such a >> platform will be created? =A0Would it even be a good idea to span >> partitions across such an arrangement given that different devices >> will behave differently? > > OK, in the example above such a spanning partition is not so likely. But = think > about my original example, the Intel P30 with two different cfi compatibl= e > chips on one die. Here a partition spanning over both devices is very lik= ely. I agree. Same thing when two or more flash chips are put on a board in consecutive addresses. I've worked on plenty of these arrangements myself. This case really does sound like a driver bug and that the existing cfi-flash binding is sufficient to describe the hardware. IIUC, when all the flash chips are of the same type the physmap_of driver should be smart enough to detect each of the flash chips within the reg range. If I'm wrong and it cannot do this, then it would be a simple matter of adding an additional tuple to reg for each discrete chip. A simple, backwards compatible extension which doesn't require a new binding. g. --=20 Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.