From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 22 May 2001 17:27:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 22 May 2001 17:27:08 -0400 Received: from router-100M.swansea.linux.org.uk ([194.168.151.17]:50436 "EHLO the-village.bc.nu") by vger.kernel.org with ESMTP id ; Tue, 22 May 2001 17:26:56 -0400 Subject: Re: alpha iommu fixes To: jlundell@pobox.com (Jonathan Lundell) Date: Tue, 22 May 2001 22:24:07 +0100 (BST) Cc: rth@twiddle.net (Richard Henderson), andrea@suse.de (Andrea Arcangeli), ink@jurassic.park.msu.ru (Ivan Kokshaysky), linux-kernel@vger.kernel.org, davem@redhat.com (David S. Miller) In-Reply-To: from "Jonathan Lundell" at May 22, 2001 02:17:21 PM X-Mailer: ELM [version 2.5 PL3] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: From: Alan Cox Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > On the main board, and not just the old ones. These days it's > typically in the chipset's south bridge. "Third-party DMA" is > sometimes called "fly-by DMA". The ISA card is a slave, as is memory, > and the DMA chip reads from one ands writes to the other. There is also another mode which will give the Alpha kittens I suspect. A few PCI cards do SB emulation by snooping the PCI bus. So the kernel writes to the ISA DMA controller which does a pointless ISA transfer and the PCI card sniffs the DMA controller setup (as it goes to pci, then when nobody claims it on to the isa bridge) then does bus mastering DMA of its own to fake the ISA dma Alan