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

Colin Ngam
2003-05-15T23:57:09Z

"David S. Miller" wrote:

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