From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 30 Oct 2007 11:58:33 +1100 From: David Gibson To: Grant Likely Subject: Re: [PATCH 05/11] [POWERPC] TQM5200 DTS Message-ID: <20071030005833.GI29263@localhost.localdomain> References: <20071023231302.29359.27417.stgit@hekate.izotz.org> <20071023231333.29359.35252.stgit@hekate.izotz.org> <13403420.post@talk.nabble.com> <4720BA4B.5090707@semihalf.com> <20071026013343.GD457@localhost.localdomain> <4725EB9E.1030507@semihalf.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Cc: linuxppc-dev@ozlabs.org, Marian Balakowicz , Martin Krause List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Oct 29, 2007 at 09:40:23AM -0600, Grant Likely wrote: > On 10/29/07, Marian Balakowicz wrote: > > David Gibson wrote: > > > On Thu, Oct 25, 2007 at 05:46:19PM +0200, Marian Balakowicz wrote: > > >> Grant Likely wrote: > > >>> On 10/25/07, Martin Krause wrote: > > > [snip] > > >>>> On a board with 16 MiB FLASH for example the "big-fs" _and_ the "misc" > > >>>> partition could not be used. "big-fs", because the memory is too small > > >>>> (which is OK) and "misc", because it overlaps 1 MiB over the physikal > > >>>> flash border. So only the first 9 MiB of the flash could be used in Linux. > > >>>> The remaining 7 MiB couldn't be accessed. > > >>> Perhaps it would be better to drop the flash layout from the in-kernel > > >>> dts files entirely since flash layout can be a fluid thing. > > >> Well, but that would not be really user friendly, I'd rather stick > > >> with some default config. > > > > > > Strictly speaking the device-tree is not the right place for flash > > > partitioning information. We put it there because it's preferable to > > > having hardcoded per-board flash layouts in the code itself. > > > > > > It only really works well, though, when there are strong conventions > > > (shared with the firmware) about how to partition the flash. > > > > > > Where it's really up to the user to determine how they want to lay out > > > their flash, putting things in the device tree isn't a really good > > > idea. > > > > In principle, you are right, we should not be putting a user dependent > > configuration into .dts files. But on the other hand, bindings have > > been defined for flash-like devices and their partition layouts and > > physmap_of device driver is expecting to get this information from the > > blob. So, it is the place for it. But if we are not to put partition > > layouts into the default kernel .dts files then we should > > provide/maintain some examples an that may be a even bigger mess. > > > > > Incidentally, it's not required that *all* the flash address space be > > > in partitions, so it is possible only give partitions for those flash > > > chunks which the firmware needs to know about. > > > > That might be nicer solution but different variants of TQM5200 boards > > do not share the same subset of partitions (default u-boot partitions > > at least), so it will not help much. > > It's probably more appropriate to have the flash partition layout in > the u-boot environment and have u-boot populate the partition > information in the device tree. That sounds like a reasonable idea. But if the flash partition layout is *not* fixed - but selectable by the board installer, then it should certainly not be hardcoded into a fixed dts. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson