linux-kernel - Re: [RFC PATCH 4/4] ARM: Xilinx: Adding Xilinx board support

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Date:	Tue, 3 May 2011 09:58:14 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	johnlinn@...cast.net, nicolas pitre <nicolas.pitre@...aro.org>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	grant likely <grant.likely@...retlab.ca>,
	john linn <john.linn@...inx.com>
Subject: Re: [RFC PATCH 4/4] ARM: Xilinx: Adding Xilinx board support

On Tuesday 03 May 2011 01:01:18 Russell King - ARM Linux wrote:
> It is preferable to use the same mapping, as it ensures that you're not
> going to create incompatible aliases.

Is aliasing a problem for MMIO mappings? I would think that you can
ioremap registers anywhere and as often as you want because they are
never cacheable.

> But, before we get too bogged down with this, please realise that it is
> possible to setup early mappings from the device tree for things like the
> SCU.  Maybe not using ioremap(), but I'm sure we can find some way to use
> the iotable_init() stuff to setup some early mappings from DT for this
> stuff.

Good point. It doesn't really matter how the entries get into the page
table, whether you call it ioremap, iotable_init, create_mapping or
ioremap_early. What matters is that we don't hardcode the physical
address in the board code, because that limits the possible reuse
on other device tree enabled targets.

	Arnd
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