Date: Wed, 12 Apr 2000 22:10:07 -0400 From: "Gary T. Corcoran" <gcorcoran@lucent.com> To: Warner Losh <imp@village.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: [Fwd: PCI DMA Questions] Message-ID: <38F52C7F.7E627B83@lucent.com> References: <38F41901.A075EAC9@home.com>
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Warner Losh wrote: > -------- Original Message -------- > Subject: PCI DMA Questions > > I'm debugging a hunk of PCI hardware that I have under NDA. It > doesn't seem to be initiating DMA transfers. This may be a hardware > problem, but before I go back to the vendor, I want to make sure that > I'm doing the DMA initialization right. It was my understanding that > DMA just happened on the PCI bus and nothing special was needed. > > Am I doing this right? Is there something unobviously named that is > used to "start" the DMA or tell some DMA controller that DMA is going > to happen? I didn't see anything in any of the pci drivers, and I > don't recall ever having to deal with this in the past. Since I didn't see much in the way of response to your questions... Now that my device driver for my bus-mastering PCI board is basically working :), I can confirm that on an x86 PC, there is nothing needed to "start" bus-mastering DMA, other than programming your bus-mastering PCI device and telling it to "go". So either you need to poke some more registers on your device :), or you've got some busted hardware... Gary To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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