From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Date: Tue, 04 Dec 2001 20:22:54 +0000 Subject: Re: [Linux-ia64] patch to no longer use ia64's software mmu Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org From: David Mosberger Date: Tue, 4 Dec 2001 08:26:59 -0800 I think the issue at hand is whether, longer term, it is desirable to move all bounce buffer handling into the PCI DMA layer or whether Linux should continue to make bounce buffer management visible to drivers. I'd be interested in hearing opinions. Well, this whole ia64 situation should be the example that shows that for severely broken 64-bit platforms, like IA64, doing the bounce buffering in the PCI DMA layer is a lose. The HIGHMEM option is the optimal one in this case, and I think that is fine. If what you are asking is should we tweak the APIs again so that situations like current IA64 can be done more sanely in the PCI DMA layer, I say definitely no. There really is no excuse for the current IA64 hardware situation, there were probably well over 3 or 4 major 64-bit platforms from competitors, whose PCI controllers were pretty well documented publicly, from which Intel could have derived a working 64-bit platform PCI controller design. When a saner IA64 hardware implementation comes about (if ever), you can make CONFIG_IA64_WHATEVER_PLATFORM which undoes the HIGHMEM stuff and enables PCI DMA support code for those chipsets. As Alan has suggested. That is a perfectly fine way of dealing with this. Franks a lot, David S. Miller davem@redhat.com