From mboxrd@z Thu Jan 1 00:00:00 1970 From: Colin Ngam Date: Fri, 16 May 2003 00:36:55 +0000 Subject: [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 "David S. Miller" wrote: > From: Colin Ngam > Date: Thu, 15 May 2003 18:57:09 -0500 > > It is in the PCI-X Spec that all PCI-X devices in PCI-X Mode have > to support DAC. > > Having to support DAC cycles does not mean that it must support full > 64-bit DMA addresses in it's descriptors. Hi David, I do not believe it is within spec to perform DAC when the Upper 32bits are 0s. Current usage of pci_alloc_consistent(), even if you want to do DAC, you cannot, because the interface is defined to return only 32bits worth of addresses. However, I think we are beyond this point now. Thanks. colin > > > A cost sensitive PCI-X device may wish to use 32-bit addressing in > it's descriptors in order to keep pin counts down etc.