From mboxrd@z Thu Jan 1 00:00:00 1970 From: Colin Ngam Date: Thu, 15 May 2003 23:57:09 +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 18:45:42 -0500 > > Something else I do not understand .. in the PCI world, what does > Physical Memory Address got to do with 32Bit Mapped DMA > Bus Address? > > Many platforms direct map, that is what I assumed was happening > here and causing the problems. > > I have not seen any of the drivers broken yet - e.g. qlXXX, acenic, > tg3 etc. > > It only works because these devices happen to allow >32-bit DMA > addresses for descriptors. You will find eventually that many > comodity pieces of PCI-X hardware will opt to only support 32-bit > DMA addressing for descriptor tables and whatnot. Hi David, It is in the PCI-X Spec that all PCI-X devices in PCI-X Mode have to support DAC. It did not say that it cannot support SAC or should not support SAC, but it has to support DAC. Thanks. colin