From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Thu, 15 May 2003 21:29:18 +0000 Subject: Re: [Linux-ia64] Re: 64 Bits DMA Addresses for Alloc Consistent Interfaces. 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 On Thu, May 15, 2003 at 01:24:12PM -0700, Jesse Barnes wrote: > > All devices I am aware of do not support 64-bit addresses for their > > descriptors, only 32-bit. > > PCI-X devices are required to support 64 bit addrs. They'll only > generate SAC if the top 32 bits are 0, but our platform is incapable > of handling this, since the IOMMU can't be used in PCI-X mode (i.e. we > need high order bits for PCI-X devices). I think you're missing Dave's point. While the card is required to support DAC that doesn't mean the device on the card is necessarily capable of being handed a full 64-bit address to DMA into. >From the way he's talking, I'd surmise tg3 is a good example -- I suspect the ring buffers only support 32-bit addresses. -- "It's not Hollywood. War is real, war is primarily not about defeat or victory, it is about death. I've seen thousands and thousands of dead bodies. Do you think I want to have an academic debate on this subject?" -- Robert Fisk