From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 23 Mar 2007 14:24:40 +1100 From: David Gibson To: Segher Boessenkool Subject: Re: [PATCH 07/17] bootwrapper: Add dt_set_memory(), to fill in the /memory node. Message-ID: <20070323032440.GD28006@localhost.localdomain> References: <20070316172641.GA29709@ld0162-tx32.am.freescale.net> <20070316172848.GG29784@ld0162-tx32.am.freescale.net> <20070317012654.GE3969@localhost.localdomain> <20070321234226.GB2295@localhost.localdomain> <7ce9c69ae76258f47790c5ceb851a355@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <7ce9c69ae76258f47790c5ceb851a355@kernel.crashing.org> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Mar 22, 2007 at 12:02:56PM +0100, Segher Boessenkool wrote: > >>> However, #address-cells=2, #size-cells=1 is common enough that we > >>> really need to support that case. > >> > >> On the root node?!? Who would do such a strange thing? > > > > Ebony, for one, it works nicely for a 32-bit system with >32-bit bus. > > It means you cannot have a 4GB-or-bigger region below your > root node. Dunno if Ebony ever needs one, for I/O mapping > perhaps? Nope. 0-4GB is RAM, 4-8 is in-built IO, 8-12 is PCI IO, and I forget what 12-16 is, if anything. > > Apple G5s do it too. > > And they do a an awful workaround for their memory node > because of this. > > Is their any reason why you couldn't use #a=#s=2 on 32-bit > systems? The root node is one contiguous hunk of address > space, so the biggest (theoretically) possible size is equal > to the biggest address (+1). It's not hard to come up with > an example where you need a size of 4GB or more. Well, yes, we could. I believe the only reason Apple does it is to make the tree a little more compact. But the point is that trees are out there with #a=2 #s=1, so the fixup code ought to be able to handle them. -- 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