PCI caching question related to mvme5500
dufault at hda.com
Tue Nov 1 20:04:21 UTC 2005
On Nov 1, 2005, at 2:50 PM, Till Straumann wrote:
> No. Currently, PCI memory space is mapped through a BAT as
> cache-inhibited/guarded. Supporting pre-fetchable memory on
> PCI devices would require
> a) setting up a second mapping marked as cacheable (BAT or
> b) reconfiguring all cacheable devices to use addresses
> mapped by a)
> c) resolving coherency issues [probably the hardest]
> Regarding b), note that it is potentially dangerous to
> simply map the same physical address range twice, i.e.,
> both, caching-inhibited and caching-allowed.
I guess I'll stick with my local hack then, which is to map cacheable
through a BAT and only access the boards sample memory there. I
don't get your note, though. What can happen if you have something
like that sample memory mapped twice?
It isn't worth signing an NDA and implementing DMA for this application.
More information about the users