Messages in this thread | | | Date | Fri, 18 Jan 2002 22:07:09 +0100 (CET) | From | Gérard Roudier <> | Subject | Re: pci_alloc_consistent from interrupt == BAD |
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On Fri, 18 Jan 2002, David S. Miller wrote:
> From: Gérard Roudier <groudier@free.fr> > Date: Fri, 18 Jan 2002 21:21:35 +0100 (CET) > > I have noted that some ports may [ever] require pci_alloc_consistent not > to be called from interrupt context. Just I will look into this when time > will allow. > > Do not bother Gerard, these ports really are broken and > pci_alloc_consistent must work from interrupts. > > I am not going to ever use not cache coherent hardware, even if I am ready > to make the sym driver work reliably on such brain-dead things. Just it is > not high priority stuff for now. > > Perhaps you misunderstand, it is not "lack of cache coherency" it is > "cache needs flushing around DMA transfers" and this is handled > perfectly by PCI DMA interfaces. It is nothing you should be > concerned about.
Depends on the OS.
Under Linux, PCI consistent allocation support is a requirement. Let me cross fingers for this to stay as it is. :)
Under some other (NetBSD, for example, just not to name it :)), such feature is just a hint and as a result drivers are theorically also required to care about cache flushing for DMAs that involve driver internal data structures if full portability is in concern. Btw, I donnot really use NetBSD O/S but just ported sym-2 to it (NetBSD-1.5 with coherency being a requirement for driver data structure allocations) as an exercise.
Gérard.
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