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

From: Jeff Garzik <>
Date: 2006-10-25 05:22:10
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.


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Received on Wed Oct 25 05:22:23 2006

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