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Message-ID: <1388707457.11795.32.camel@snotra.buserror.net>
Date: Thu, 2 Jan 2014 18:04:17 -0600
From: Scott Wood <scottwood@...escale.com>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC: Nikita Yushchenko <nyushchenko@....rtsoft.ru>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Arnd Bergmann <arnd@...db.de>,
Dmitry Krivoschekov <dkrivoschokov@....rtsoft.ru>,
"Alexey Lugovskoy" <lugovskoy@....rtsoft.ru>,
Thierry Reding <thierry.reding@...onic-design.de>,
<linux-kernel@...r.kernel.org>,
"Rob Herring" <robherring2@...il.com>,
Grant Likely <grant.likely@...aro.org>,
<linuxppc-dev@...ts.ozlabs.org>
Subject: Re: commit e38c0a1f breaks powerpc boards with uli1575 chip
On Mon, 2013-12-30 at 14:13 +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2013-12-19 at 08:42 +0400, Nikita Yushchenko wrote:
> > No, this does not help.
> >
> > I've dumped the actual content of 'range' and 'addr' at the failure
> > point
> > (i.e. ar point that returns error with e38c0a1f but passes without
> > e38c0a1f ):
> >
> > OF: default map, cp=0, s=10000, da=70
> > range: 01 00 00 00 00 00 00 00 00 00 00 00
> > addr: 00 00 00 00 00 00 00 00 00 00 00 70
>
> Something that has a #address-cells larger than 2, or more generally,
> an address field that contains more than a single number, must have
> a specific translation backend, like we have for PCI.
>
> This is a bit annoying but originates from the original OFW stuff on
> which this stuff is based where the bus node would provide the methods
> for translation.
I can maybe see that for PCI which has a special encoding, but why is it
always needed? E.g. if Freescale localbus had a 64-bit offset instead
of 32-bit, the child nodes would have 3 address cells, but
straightforward use of ranges would bring it down to 2 for the final
physical address. Existing localbus nodes already have "an address
field that contains more than a single number"; it's just a simple
enough encoding that it works to treat it as if it were a single large
number.
-Scott
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