From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Higdon Date: Fri, 16 May 2003 06:47:55 +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 On Thu, May 15, 2003 at 01:07:39PM -0700, David S. Miller wrote: > From: Colin Ngam > Date: Thu, 15 May 2003 08:17:58 -0500 > > Anyway, to make a long story short, we like to "extend" these > interfaces to return DMA addresses of 64 bits if and when the > driver has the full capabality to support DAC - via it's > DMA mask capability setting. > > All devices I am aware of do not support 64-bit addresses for their > descriptors, only 32-bit. The Qlogic and LSI Logic SCSI and FC devices support 64 bit addresses for their descriptors. Also the old Adaptec (now JNI) 1160. I do not believe this is unusual. Certainly all PCI-X devices should support 64 bit addresses for descriptors. The Tigon3 supports 64 bit addresses for descriptors. > There is a huge difference between using a "64-bit address" and > requiring to generate a DAC cycle, the latter of which is > probably what you need and that is independant of what kind of > address pci_alloc_consistent() is giving you. Not independent. Because if pci_alloc_consistent gives an address in which any of bits 32-63 are set, then the adapter will use a DAC to access the descriptor. I guess you're saying that some adapters may support more than 32 bits but fewer than 64. Such devices would not work on our platform. Which PCI-X devices do not support the full 64 bit address space? I don't know of any. jeremy