allocating uncachable memory

Ronald Wahl rwa at
Fri Aug 25 17:12:06 EST 2000

On Thu, 24 Aug 2000, Ronald Wahl wrote:

> On Wed, 23 Aug 2000, Dan Malek wrote:
> > Benjamin Herrenschmidt wrote:
> >
> > > ... 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?


** Sent via the linuxppc-dev mail list. See

More information about the Linuxppc-dev mailing list