updating the GTT and flushing the AGP TLB by storing the GTT in
write-combining memory.
On x86 flushing the AGP TLB is done by an I/O operation or a store to a
MMIO register in uncacheable memory. Both cases imply that WC buffers are
flushed so no memory barriers are needed.
On powerpc there is no WC memory type. It maps to uncacheable memory and
two stores to uncacheable memory, such as to the GTT and then to an MMIO
register, are strongly ordered, so no memory barriers are needed either.
MFC after: 1 month
bumped to 800004 to note the change though userland apps should not be
affected since they use <sys/agpio.h> rather than the headers in
sys/dev/agp.
Discussed with: anholt
Repocopy by: simon
/dev/agpgart and agp_free_res() frees resources like the BAR for the
aperture. Splitting this up lets chipset-specific detach routines
manipulate the aperture during their detach routines without panicing.
MFC after: 1 week
Reviewed by: anholt
attach to the hostb driver instead. This means that agp can now be loaded
at runtime (in theory at least). Also, the drivers no longer have to
explicity call device_verbose() to cancel out any earlier calls to
device_quiet() by the hostb(4) driver (this shows a limitation in new-bus,
drivers really shouldn't be doing device_quiet() until they know they are
going to drive that device, i.e. in attach).
the Linux driver, since specs are unavailable. Many thanks to Adam Kirchhoff
for multiple useful testing cycles, and Ralf Wostrack for the final fix to get
it working.
PR: i386/75251
Submitted by: anholt
