[Linux-ia64] Re: 64 Bits DMA Addresses for Alloc Consistent Interfaces.

David S. Miller
2003-05-15T23:46:19Z

From: Colin Ngam <cngam@sgi.com>
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.