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

Russell King - ARM Linux
2011-05-03T08:52:50Z

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.