Date: Tue, 22 Mar 2011 20:12:19 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Matthew Fleming <mdf356@gmail.com> Cc: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: DMA controller on Northbridge? Message-ID: <20110322181219.GU78089@deviant.kiev.zoral.com.ua> In-Reply-To: <AANLkTinjmMtF=qrNCXJ84Wir0AYErtCdZ5LeLFOPJeFg@mail.gmail.com> References: <AANLkTinjmMtF=qrNCXJ84Wir0AYErtCdZ5LeLFOPJeFg@mail.gmail.com>
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--J7e1NV0wt6ySF7jo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 22, 2011 at 10:11:04AM -0700, 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? >=20 > 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. >=20 > 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? :-) >=20 > Attached is the boot dmesg; I can also run pciconf commands, etc., to > help out with figuring out what I have. I believe what are you looking for is ftp://download.intel.com/technology/.../Intel(r)_VT_for_Direct_IO.pdf On my X58 machine it is shown like this: none6@pci0:0:22:2: class=3D0x088000 card=3D0xf38015d9 chip=3D0x34328086 r= ev=3D0x12 hdr=3D0x00 vendor =3D 'Intel Corporation' device =3D 'DMA Engine' class =3D base peripheral cap 11[80] =3D MSI-X supports 1 message in map 0x10 cap 10[90] =3D PCI-Express 2 root endpoint max data 128(128) link x0(x0) cap 01[e0] =3D powerspec 3 supports D0 D3 current D0 --J7e1NV0wt6ySF7jo Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk2I5oMACgkQC3+MBN1Mb4gUeACeL42bSSf4wYnuIln1Coyq8gMK 24EAoLwk/hrrVsfObn91pUQpqlw9ZiSN =ux7n -----END PGP SIGNATURE----- --J7e1NV0wt6ySF7jo--
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