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Message-id: <alpine.LFD.2.02.1110141353390.17040@xanadu.home>
Date: Fri, 14 Oct 2011 14:01:07 -0400 (EDT)
From: Nicolas Pitre <nico@...xnic.net>
To: Arnd Bergmann <arnd@...db.de>
Cc: Stephen Warren <swarren@...dia.com>,
Russell King - ARM Linux <linux@....linux.org.uk>,
Olof Johansson <olof@...om.net>,
Peter De Schrijver <pdeschrijver@...dia.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
"Colin Cross (ccross@...roid.com)" <ccross@...roid.com>,
Erik Gilling <konkers@...roid.com>
Subject: Re: [PATCH] arm/tegra: select AUTO_ZRELADDR by default
On Fri, 14 Oct 2011, Arnd Bergmann wrote:
> On Friday 14 October 2011, Stephen Warren wrote:
> > Arnd Bergmann wrote at Friday, October 14, 2011 9:30 AM:
> > ...
> > > You mention that tegra30 will require AUTO_ZRELADDR.
> >
> > Well, just to be clear, here's the situation I think:
> >
> > Tegra20's SDRAM starts at physical address 0.
> >
> > Tegra30's SDRAM starts at physical address 2G.
> >
> > To support that, we could either:
> >
> > a) Introduce a new Kconfig variable for Tegra30, make T20/T30 mutually
> > exclusive, and update arch/arm/mach-tegra/Makefile.boot to set zreladdr
> > etc. based on the new Tegra30 config variable too. Then, there's no need
> > for AUTO_ZRELADDR anywhere.
> >
> > b) Have no new config variable, build a unified T20/T30 kernel, leave
> > Makefile.boot untouched, and rely on using AUTO_ZRELADDR for Tegra30 to
> > account for the different SDRAM physical addresses.
>
> Ok, thanks for the explanation, that makes it much clearer. For
> completeness, you could also do both of the above and make T20/T30 mutually
> exclusive unless AUTO_ZRELADDR is set. That might be more complex than
> necessary, I don't know.
The way I'm restructuring things around this is that AUTO_ZRELADDR will
always be active by default, just like ARM_PATCH_PHYS_VIRT now. This
platform specific exclusion thinking is a step backward so I'd prefer if
people would refrain from going there for the moment.
Nicolas
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