Messages in this thread | | | Subject | Re: [RFC] I/O Access Abstractions | Date | Tue, 3 Jul 2001 12:53:14 +0100 (BST) | From | Alan Cox <> |
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> For example, one board I've got doesn't allow you to do a straight > memory-mapped I/O access to your PCI device directly, but have to reposition a > window in the CPU's memory space over part of the PCI memory space first, and > then hold a spinlock whilst you do it.
What does this prove. PA-RISC has this problem in reverse for I/O cycle access to PCI slots on hppa1.1 at least. Cookies work _fine_
And by the time you are taking a spinlock who cares about the add, you can do that while the bus transactions for the atomic op are completing
On the other hand each call, each push of resource * pointers costs real clocks on x86
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