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

Matthew Wilcox
2003-05-15T21:29:18Z

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.

--
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