Re: [Fwd: Re: [PATCH 0/5]PCI: x86 MMCONFIG]

[Robert Hancock]

Tony Camuso wrote:
> Robert Hancock wrote:
>
> > First off, I would like to see confirmation from the horses's mouths 
> > here (namely AMD, ServerWorks/Broadcom, and whoever else) that there 
> > is no other way to get around this problem than disabling MMCONFIG for 
> > accesses behind those chips.
>
> I happen to have this one stored in my desktop.
>
>  From AMD-8132TM HyperTransportTM
>      PCI-X®2.0 Tunnel
>       Revision Guide
>
> http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/30801.pdf 
>
>
> 79 AMD-8132TM Tunnel Lacks Extended Configuration
>         Space Memory-Mapped I/O Base Address Register
>
> Description
>
> Current AMD processors do not natively support PCI-defined extended 
> configuration space. A memory
> mapped I/O base address register (MMIO BAR) is required in chipset 
> devices to support extended
> configuration space. The AMD-8132 does not have this MMIO BAR.
> Potential Effect On System
>
> The AMD-8132 is a PCI-X® Mode 2 capable device and requires the MMIO BAR 
> to support extended
> configuration space. Using a device which does have this MMIO BAR and an 
> AMD-8132 on the same
> HyperTransportTM link of the processor may cause firmware/software 
> problems.
>
> The base configuration space of the AMD-8132 and PCI(-X) devices 
> attached to it are accessible using only
> the mechanism defined in PCI 2.3. Registers of PCI-X Mode 2 devices 
> attached to the AMD-8132 in the
> extended configuration space are not accessible. The AMD-8132 has no 
> registers in the extended
> configuration space.
>
> Suggested Workaround
>
> It is strongly recommended that system designers do not connect the 
> AMD-8132 and devices that use extended
> configuration space MMIO BARs (ex: HyperTransport-to-PCI Express® 
> bridges) to the same processor
> HyperTransport link.
>
> Fix Planned
> No

That does sound fairly definitive. I have to wonder why certain system 
designers then didn't follow their strong recommendation..

--
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@xxxxxxxxxxxxx
Home Page: http://www.roberthancock.com/

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