865. The APSIZE register has a variable-sized field of enabled bits.
To figure out how many bits a specific host bridge supports, write the
maximum width and see how many bits are set in the hardware. We then
use this mask for setting and getting the aperture size. Prior to this,
the agp(4) driver would treat an aperture size of 256 MB as 128 MB and
would not allocate enough physical memory for the GART as a result.
MFC after: 3 days
Sponsored by: The Weather Channel
Approved by: re (rwatson)
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