From owner-freebsd-hackers Wed Apr 12 20: 0:55 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from hoemlsrv.firewall.lucent.com (hoemail1.lucent.com [192.11.226.161]) by hub.freebsd.org (Postfix) with ESMTP id A437337B691 for ; Wed, 12 Apr 2000 20:00:52 -0700 (PDT) (envelope-from gcorcoran@lucent.com) Received: from hoemlsrv.firewall.lucent.com (localhost [127.0.0.1]) by hoemlsrv.firewall.lucent.com (Pro-8.9.3/8.9.3) with ESMTP id XAA16846 for ; Wed, 12 Apr 2000 23:00:51 -0400 (EDT) Received: from mhmail.mh.lucent.com (h135-3-115-8.lucent.com [135.3.115.8]) by hoemlsrv.firewall.lucent.com (Pro-8.9.3/8.9.3) with ESMTP id XAA16827; Wed, 12 Apr 2000 23:00:51 -0400 (EDT) Received: from lucent.com by mhmail.mh.lucent.com (8.8.8+Sun/EMS-1.5 sol2) id WAA22321; Wed, 12 Apr 2000 22:01:57 -0400 (EDT) Message-ID: <38F52C7F.7E627B83@lucent.com> Date: Wed, 12 Apr 2000 22:10:07 -0400 From: "Gary T. Corcoran" Organization: Lucent Microelectronics - Modem and Multimedia Systems X-Mailer: Mozilla 4.06 [en] (Win98; U) MIME-Version: 1.0 To: Warner Losh , FreeBSD Hackers Subject: Re: [Fwd: PCI DMA Questions] References: <38F41901.A075EAC9@home.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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