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

From: Matthew Wilcox <>
Date: 2003-05-16 07:29:18
On Thu, May 15, 2003 at 01:24:12PM -0700, Jesse Barnes wrote:
> > All devices I am aware of do not support 64-bit addresses for their
> > descriptors, only 32-bit.
> PCI-X devices are required to support 64 bit addrs.  They'll only
> generate SAC if the top 32 bits are 0, but our platform is incapable
> of handling this, since the IOMMU can't be used in PCI-X mode (i.e. we
> need high order bits for PCI-X devices).

I think you're missing Dave's point.  While the card is required to
support DAC that doesn't mean the device on the card is necessarily
capable of being handed a full 64-bit address to DMA into.

>From the way he's talking, I'd surmise tg3 is a good example -- I suspect
the ring buffers only support 32-bit addresses.

"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk
Received on Thu May 15 14:30:30 2003

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