[LinuxBIOS] MB1030 / 3036 VGA: disabling 00:12:4

Goodrich,Steven steven.goodrich at amd.com
Fri Apr 28 22:37:54 CEST 2006

I've looked at the original BIOS source and the internal versions of the
documentation, and here's what I've determined:  As near as I can tell,
you cannot disable the PCI header for the device at 00:12:4.  The
original BIOS (written by others on the BIOS team here at AMD in
Colorado) virtualized the PCI headers via SMM code, and that header was
masked when internal graphics were disabled.  Without SMM code, you
cannot do the same thing.
Interesting info/notes:
If you disable memory space via the PCI header (PCI header register 04,
bit 1 -- clear to zero), you should disable it somewhat.
If the F4 Video Configuration trap bit (F0, Index 42h, bit 1) is set,
the system will generate SMIs when trying to access the PCI header
registers.  This should be clear for a non-SMM system.
I suppose you could special-case the device in your PCI scan/enumeration
code, but that is probably more kludgy than you'd like.  Could you
reduce the device's resource requirements to zero?

    -- Steve G.

Steve Goodrich (Steven.Goodrich at amd.com <mailto:Steven.Goodrich at amd.com>
Advanced Micro Devices, Inc.
1351 S. Sunset Street
Mail Stop 83-36
Longmont, CO  80501
303-774-5129    (fax: 303-774-5801)

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