Correct PCI suspend and resume operations

[M. Warner Losh]

In message: <200306101644.h5AGiawR066527 at puma.icir.org>
            Orion Hodson <orion at freebsd.org> writes:
: It looks like the pci configuration space state has been lost during
: the suspend and resume.  This may be because the bus has removed power
: from the devices attached to it on suspend.

During a suspend, devices are typically set into D3 state.  Transition
from D3 -> D0 resets the most of the config space.

: I've been through a cross section of drivers this morning and some
: explicitly save and restore the PCI configuration state space and
: others don't.  The former seems like the safest path in most cases.
: AFAICT, we don't common code for handling this and maybe there should
: be some rather than have each driver replicate this behaviour.

This should be saved in the pci bus layer.  I have some very imperfect
patches in my p4 tree that I'm working on.

Warner