Re: Flushing writes to PCI devices

Bryan O'Sullivan
2006-09-21T21:04:03Z

On Thu, 2006-09-21 at 13:56 -0700, Roland Dreier wrote:
> Bryan> Yes. If your device requires that writes to some locations
> Bryan> in MMIO space be performed in a specific order, you must
> Bryan> explicitly do this in your driver. Intel CPUs will flush
> Bryan> posted writes out of order, for example.
>
> Really? Just normal posted PCI writes without using MTRRs or
> write-combining or anything like that?

No, not normal writes, but if you're writing to an area where you've
enabled write combining, it will happen (but not IIRC on AMD x86_64
CPUs). Sorry for the lack of clarity.

<b