So pci_raw_set_power_state() does a pci_read_config_word() and that returns a
valid word. Yet, the device appears to be not in powerd up state later on.
How's that possible, and why does it work on Windows?

Can I inspect Windows behavior in some way to get insight?

Since Windows works I'm sure there must be a SW fix (or at least a workaround)
available. Perhaps just wait for a bit?