Re: allocating uncachable memory

On Thu, 24 Aug 2000, Ronald Wahl wrote:

On Wed, 23 Aug 2000, Dan Malek wrote:

quoted

Benjamin Herrenschmidt wrote:

quoted

... Most PPC machines out there (all PCI PPC machines) are,
AFAIK, cache coherents. PPC NuBus powermacs are not.

The MPC8xx and IBM 4xx systems can have PCI options but are not
cache coherent.  PCI masters are still challenging (if you can actually
get them to work :-).

It's an MPC860 together with an PLX 9054 PCI Controller. The effect is
that most of the data is correct but sometimes the MPC860 seems to get
wrong data. Looks like more than a race condition than a cache side
effect, but I'm not sure.

After some further tests I found out that it is the data cache of the
MPC860. If I switch the data cache off in head.S all goes well. So my
question again: How can I get an alias mapping (with _PAGE_NO_CACHE |
_PAGE_GUARDED) of some already mapped pages.
...or can I mark pages as non-cacheable w/o alias mapping?

thx,
ron


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