Date: Tue, 22 Mar 2011 12:32:16 -0500 From: Mark Tinguely <marktinguely@gmail.com> To: freebsd-hackers@freebsd.org Subject: Re: DMA controller on Northbridge? Message-ID: <4D88DD20.7020104@gmail.com> In-Reply-To: <AANLkTinjmMtF=qrNCXJ84Wir0AYErtCdZ5LeLFOPJeFg@mail.gmail.com> References: <AANLkTinjmMtF=qrNCXJ84Wir0AYErtCdZ5LeLFOPJeFg@mail.gmail.com>
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On 3/22/2011 12:11 PM, Matthew Fleming wrote: > How can I tell if the Northbridge on a machine has a built-in DMA > controller? And if it does, what device would I use to control it? > > I ask because I'm working with a PCI card that has a 36-bit physical > address limit, and that means bounce buffers when using more than 64GB > of memory. I'd prefer not to use bounce buffers, and since the card's > memory that I'm using is mapped into the physical space of the FreeBSD > host, the entire address space of the card that I care about is > available to FreeBSD. So while pio to the card's memory is too slow > to be useful, if there was a way to use a DMA controller on the > motherboard to get data into and out of the card, that may be > preferable to using the card's DMAC with the limited address space. > > But all that's just theory -- I have no idea how to tell whether the > mobo has a DMAC, and if it does, how to control it. Help? :-) > > Attached is the boot dmesg; I can also run pciconf commands, etc., to > help out with figuring out what I have. > > Thanks, > matthew > > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" Sounds like you are referring to IOMMU: http://software.intel.com/en-us/blogs/2009/03/02/intels-virtualization-for-directed-io-aka-iommu-part-1/ --Mark Tinguely
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