Re: Ordering between PCI config space writes and MMIO reads?

Jeff Garzik
2006-10-24T19:22:10Z

On Tue, Oct 24, 2006 at 12:13:19PM -0700, Roland Dreier wrote:
> 1) Is this something that should be fixed in the driver? The PCI
> spec allows MMIO cycles to start before an earlier config cycle
> completed, but do we want to expose this fact to drivers? Would
> it be better for ia64 to use some sort of barrier to make sure
> pci_write_config_xxx() is strongly ordered with MMIO?

The PCI config APIs have traditionally enforced very strong ordering.
Heck, the PCI config APIs often take a spinlock on each read or write;
so they are definitely not intended to be as fast as MMIO.

Jeff