tree 99f4debab0f1916b1d7c0f40f0edba50d3151de6
parent 39fcde41f1bc655fac366738a2480213c3bcef35
author Barret Rhoden <brho@cs.berkeley.edu> 1565796615 -0400
committer Barret Rhoden <brho@cs.berkeley.edu> 1565796970 -0400

pci: add support for MMIO config space

MMIO config space has two benefits: it does not require the global PCI
lock, and it easily works with extended PCI config space (i.e. above 255).

For whatever reason, I had an old note that said you could use PIO for
the extended config space.  I probably got that from looking at Linux or
something.  It might have worked on some older machines for me; I don't
recall.  But it certainly does not work with all machines.  Maybe it was
an AMD/Intel thing.

I left support for PIO in case we run into a weird machine that doesn't
have the ACPI MCFG table or for debugging.  Though even my QEMU has an
MCFG.  We can remove it if it is a pain - maybe when we make PCI more
architecture-independent.  Right now it is x86-specific, both in PIO and
MMIO ops.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>