[POWERPC] Cope with PCI host bridge I/O window not starting at 0

Currently our code to set up the data structures for a PCI host bridge
and create the mapping for its I/O window assumes that the window
starts at I/O port 0 on the PCI side.  If this is not true, we can end
up with I/O port numbers in the resources for PCI devices which will
cause an oops if a driver tries to access them via inb/outb etc.,
because there is no mapping for the corresponding addresses.

Normally the I/O window starts at 0, but there are some situations on
partitioned machines with a hypervisor where the window may not start
at 0.

This fixes the problem by allocating space for the range from 0 to the
end of the I/O window.  That is, hose->io_base_virt contains the
virtual address for I/O port 0 on the PCI bus, and thus the assumption
that hose->io_base_virt - pci_io_base is the offset between the
"global" I/O port numbers (those in the PCI device resources) and the
I/O port numbers on the PCI bus is maintained.

For PCI host bridges that are present at boot, we only map the portion
of that range that correspond to the bridge's I/O window.  For bridges
added after boot we ioremap the range from 0 to the end of the I/O
window, for now; in fact hot-added bridges should be using
reserve_phb_iospace() and __ioremap_explicit (so they get sensible
global port numbers), but we don't have the infrastructure yet to do
that (basically a free_phb_iospace() routine plus appropriate
locking).

Interestingly, this makes the two arms of the if statement in
get_bus_io_range do almost exactly the same thing; that function could
now be simplified in a further patch.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/pci_64.c

@@ -1006,8 +1006,9 @@ void __devinit pci_process_bridge_OF_ranges(struct pci_controller *hose,
 
 		switch ((pci_space >> 24) & 0x3) {
 		case 1:		/* I/O space */
-			hose->io_base_phys = cpu_phys_addr;
-			hose->pci_io_size = size;
+			hose->io_base_phys = cpu_phys_addr - pci_addr;
+			/* handle from 0 to top of I/O window */
+			hose->pci_io_size = pci_addr + size;
 
 			res = &hose->io_resource;
 			res->flags = IORESOURCE_IO;
@@ -1117,8 +1118,8 @@ static int get_bus_io_range(struct pci_bus *bus, unsigned long *start_phys,
 	} else {
 		/* Root Bus */
 		res = &hose->io_resource;
-		*start_phys = hose->io_base_phys;
-		*start_virt = (unsigned long) hose->io_base_virt;
+		*start_phys = hose->io_base_phys + res->start;
+		*start_virt = (unsigned long) hose->io_base_virt + res->start;
 		if (res->end > res->start)
 			*size = res->end - res->start + 1;
 		else {