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

From: Colin Ngam <cngam_at_sgi.com>
Date: 2003-05-16 09:57:09
"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
Received on Thu May 15 17:14:35 2003

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