MIPS: PCI: Add a hook for IORESOURCE_BUS in pci_controller/bridge_controller

On SGI Origin 2k/Onyx2 and SGI Octane systems, there can exist multiple PCI
buses attached to the Xtalk bus.  The current code will stop counting PCI buses
after it finds the first one.  If one installs the optional PCI cardcage
("shoebox") into these systems, because of the order of the Xtalk widgets, the
current PCI code will find the cardcage first, and fail to detect the BaseIO
PCI devices, which are on a higher Xtalk widget ID.

This patch adds the hooks needed for resolving this issue in the IP27 PCI code
(in a later patch).

Verified on both an SGI Onyx2 and an SGI Octane.
Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Cc: Linux MIPS List <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/9074/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/pci.h

@@ -35,6 +35,8 @@ struct pci_controller {
 	struct resource *io_resource;
 	unsigned long io_offset;
 	unsigned long io_map_base;
+	struct resource *busn_resource;
+	unsigned long busn_offset;
 
 	unsigned int index;
 	/* For compatibility with current (as of July 2003) pciutils

arch/mips/include/asm/pci/bridge.h

@@ -835,6 +835,7 @@ struct bridge_controller {
 	struct pci_controller	pc;
 	struct resource		mem;
 	struct resource		io;
+	struct resource		busn;
 	bridge_t		*base;
 	nasid_t			nasid;
 	unsigned int		widget_id;

arch/mips/pci/pci.c

@@ -91,7 +91,10 @@ static void pcibios_scanbus(struct pci_controller *hose)
 
 	pci_add_resource_offset(&resources,
 				hose->mem_resource, hose->mem_offset);
-	pci_add_resource_offset(&resources, hose->io_resource, hose->io_offset);
+	pci_add_resource_offset(&resources,
+				hose->io_resource, hose->io_offset);
+	pci_add_resource_offset(&resources,
+				hose->busn_resource, hose->busn_offset);
 	bus = pci_scan_root_bus(NULL, next_busno, hose->pci_ops, hose,
 				&resources);
 	if (!bus)