From mboxrd@z Thu Jan  1 00:00:00 1970
From: Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
Subject: Re: [RFC PATCH 4/4] ARM: Xilinx: Adding Xilinx board support
Date: Tue, 3 May 2011 09:52:20 +0100
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To: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Cc: nicolas pitre <nicolas.pitre-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, johnlinn-Wuw85uim5zDR7s880joybQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
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On Tue, May 03, 2011 at 09:58:14AM +0200, Arnd Bergmann wrote:
> 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.

Provided the type and sharability is identical then there is no problem.
I wasn't referring to multiple ioremap()s of the same region - that
should be fine as the same attributes will be used.  If you mix ioremap()
and iotable_init() then you _could_ have problems if you don't use
MT_DEVICE in the iotable.

What I'm basically saying is that mixing the methods of creating these
mappings makes it much easier to get tripped up over these issues.