[RFC][PATCH] initial port of fixmap over from x86 for ppc32

[Kumar Gala]

On Apr 7, 2008, at 6:51 PM, Benjamin Herrenschmidt wrote:
>
> On Mon, 2008-04-07 at 11:20 -0500, Scott Wood wrote:
>>
>> Another possible use is a BAT/TLB1 mapping for SoC registers (or
>> anything
>> else on the board which is frequently accessed), which can be reused
>> by
>> ioremap() to avoid wasting normal TLB entries, and to facilitate  
>> early
>> debugging.
>
> As far as the above is concerned, I'm not too fan of fixed virtual
> addresses. I'd rather dynamically assign it. But we can do it.

I'm in agreement with Ben here.  On Freescale parts that could mean  
using up to 16M of virtual address space while in reality we may only  
need a handful of 4k pages to cover SoC registers that we are truly  
accessing at runtime.

However I think there might be some utility to have an early ioremap  
mappings for debug.

- k