SCU registers mapping for CA9/CA5 cores

Russell King - ARM Linux linux at arm.linux.org.uk
Mon Jun 24 05:06:41 EDT 2013


On Fri, Jun 21, 2013 at 11:29:22AM +0200, Arnd Bergmann wrote:
> I think we could actually move everything between VMALLOC_END and
> ffff0000 /into/ a larger fixmap. This would be a substantial change,
> but it would give us more vmalloc space for most configurations
> and more flexibility with what else we could put into fixmap.

... at the expense of:
(a) having to look up the PTE table pointer every time we want to add or
remove a mapping,
(b) wasting the top 15 pages from being used.

Also, the placement of some of these pages _matters_ especially for the
VIPT aliasing caches, where cache colouring becomes important.  So an
enum in fixmap isn't going to work for those.

Really, the value to such a change is very low and is really just churn
for churn's sake.  "Oh we can do something different!"  No.



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