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Subject: Re: [PATCH 15/16] Add device tree for Ebony
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
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Date: Fri, 16 Feb 2007 07:43:49 +1100
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Cc: linuxppc-dev@ozlabs.org, Yoder Stuart-B08248 <stuart.yoder@freescale.com>,
	David Gibson <david@gibson.dropbear.id.au>
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On Thu, 2007-02-15 at 15:52 +0100, Segher Boessenkool wrote:
> >>> No, the DCR tree, like the interrupt tree in most cases, is
> >>> independent of the main tree structure.
> >>
> >> Yes true; you can hang the UICs from somewhere under the
> >> "soc" node or whatever you want.  You need some way to
> >> distinguish separate identical devices though; you can't
> >> do it by device unit since your devices don't have any
> >> (they don't have a "reg" but only a "dcr-reg").  If you
> >> would hang them in a DCR tree, you could use the plain
> >> "reg" property instead of the "dcr-reg" property and
> >> all would be fine (if the DCR binding allows this -- and
> >> it better should, it is the standard OF addressing algorithm).
> >
> > It's not as DCRs are orthogonal to the normal bus tree (yeah, it sucks
> > but that's how it is, broken by design :-)
> 
> Of course, I know that.  What I'm saying is that devices
> where the *only* connection to the system is the DCR ring,
> should use normal "reg" properties instead of "dcr-reg"
> properties (and normal parent instead of "dcr-parent") to
> describe the DCR registers, so that they get a valid unit
> address.

So you say that we shold have 2 different ways to encode a DCR mapping ?
Nah ....

Ben.