The pci bus driver handles the power state, it also manages
configuration state saving and restoring for its child devices. Thus a
PCI device driver does not have to worry about those things. In fact, I
observe a hard system hang when trying to suspend a system with active
radeonkms driver where both the bus driver and radeonkms driver try to
do the same thing. I suspect that it could be because of an access to a
PCI configuration register after the device is placed into D3 state.
Reviewed by: dumbbell, jhb
MFC after: 13 days
Differential Revision: https://reviews.freebsd.org/D3561
8f875df090