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SubjectRe: NatSemi Geode improvement
On Tue, 2002-10-22 at 01:12, Hiroshi Miura wrote:
> It means that mmio must map to over 1GB area or disable this feature.

You need to think about bus mastering devices as well. With re-ordering
enabled you may confuse bus master hardware by writing fields in the
wrong order (as the PCI device sees it).

This is not a big problem. On the winchip we avoid this by using locked
operations at the end of each of the PCI DMA mapping functions. I think
all that is needed is to also define CONFIG_X86_OOSTORE for a Geode
target. The kernel will then generate

lock; addl $0, 0(%%esp)

to force write ordering where it might be essential, and if OOSTORE is
defined we can safely turn on the speed up.

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