From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Date: Thu, 15 May 2003 23:46:19 +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 From: Colin Ngam Date: Thu, 15 May 2003 18:25:54 -0500 Actually, our system does not have Physical Memory Address smaller than 48Bits - give or take couple bits ... Hence, 32Bits Mapped DMA address maps to 48Bits System Physical Address. If you support mapping 32-bit DMA bus spaces to the full 48-bit physical memory spaces, then why do you even need >4GB addressing? Saying that PCI-X devices can only generate DAC cycles is bogus, I have PCI-X tg3 cards in my systems and they function just fine. Or does this rule only apply when the device is on a PCI-X bus? This all sounds seriously broken to me, I thought the issue was that a) the addresses could not be translated, it was direct phys-->virt and b) you can't guarentee that the physical address of memory allocated on any particular node is <4GB.