Messages in this thread | | | Date | Wed, 20 Sep 2006 17:22:43 -0600 | From | Robert Hancock <> | Subject | Re: Flushing writes to PCI devices |
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Alan Stern wrote: > I've heard that to insure proper synchronization it's necessary to flush > MMIO writes (writel, writew, writeb) to PCI devices by reading from the > same area. Is this equally true for I/O-space writes (inl, inw, inb)? > What about configuration space writes (pci_write_config_dword etc.)?
Technically, according to the PCI specification, I/O space writes may be posted in the host bus bridge (though unlike MMIO space, not at any other PCI bridges) and would require a read in order to flush them. However, there seem to be few if any chipsets ever made which actually do this for I/O writes, and most code in the kernel seems to just assume it won't happen, so it's probably safe to assume the same.
-- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/
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