ppc64: Set up PCI tree from Open Firmware device tree

This adds code which gives us the option on ppc64 of instantiating the
PCI tree (the tree of pci_bus and pci_dev structs) from the Open
Firmware device tree rather than by probing PCI configuration space.
The OF device tree has a node for each PCI device and bridge in the
system, with properties that tell us what addresses the firmware has
configured for them and other details.

There are a couple of reasons why this is needed.  First, on systems
with a hypervisor, there is a PCI-PCI bridge per slot under the PCI
host bridges.  These PCI-PCI bridges have special isolation features
for virtualization.  We can't write to their config space, and we are
not supposed to be reading their config space either.  The firmware
tells us about the address ranges that they pass in the OF device
tree.

Secondly, on powermacs, the interrupt controller is in a PCI device
that may be behind a PCI-PCI bridge.  If we happened to take an
interrupt just at the point when the device or a bridge on the path to
it was disabled for probing, we would crash when we try to access the
interrupt controller.

I have implemented a platform-specific function which is called for
each PCI bridge (host or PCI-PCI) to say whether the code should look
in the device tree or use normal PCI probing for the devices under
that bridge.  On pSeries machines we use the device tree if we're
running under a hypervisor, otherwise we use normal probing.  On
powermacs we use normal probing for the AGP bridge, since the device
for the AGP bridge itself isn't shown in the device tree (at least on
my G5), and the device tree for everything else.

This has been tested on a dual G5 powermac, a partition on a POWER5
machine (running under the hypervisor), and a legacy iSeries
partition.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/ppc64/kernel/pSeries_setup.c

@@ -590,6 +590,13 @@ static int pseries_shared_idle(void)
 	return 0;
 }
 
+static int pSeries_pci_probe_mode(struct pci_bus *bus)
+{
+	if (systemcfg->platform & PLATFORM_LPAR)
+		return PCI_PROBE_DEVTREE;
+	return PCI_PROBE_NORMAL;
+}
+
 struct machdep_calls __initdata pSeries_md = {
 	.probe			= pSeries_probe,
 	.setup_arch		= pSeries_setup_arch,
@@ -597,6 +604,7 @@ struct machdep_calls __initdata pSeries_md = {
 	.get_cpuinfo		= pSeries_get_cpuinfo,
 	.log_error		= pSeries_log_error,
 	.pcibios_fixup		= pSeries_final_fixup,
+	.pci_probe_mode		= pSeries_pci_probe_mode,
 	.irq_bus_setup		= pSeries_irq_bus_setup,
 	.restart		= rtas_restart,
 	.power_off		= rtas_power_off,

arch/ppc64/kernel/pmac_setup.c

@@ -477,6 +477,18 @@ static int __init pmac_probe(int platform)
 	return 1;
 }
 
+static int pmac_probe_mode(struct pci_bus *bus)
+{
+	struct device_node *node = bus->sysdata;
+
+	/* We need to use normal PCI probing for the AGP bus,
+	   since the device for the AGP bridge isn't in the tree. */
+	if (bus->self == NULL && device_is_compatible(node, "u3-agp"))
+		return PCI_PROBE_NORMAL;
+
+	return PCI_PROBE_DEVTREE;
+}
+
 struct machdep_calls __initdata pmac_md = {
 #ifdef CONFIG_HOTPLUG_CPU
 	.cpu_die		= generic_mach_cpu_die,
@@ -488,6 +500,7 @@ struct machdep_calls __initdata pmac_md = {
 	.init_IRQ		= pmac_init_IRQ,
 	.get_irq		= mpic_get_irq,
 	.pcibios_fixup		= pmac_pcibios_fixup,
+	.pci_probe_mode		= pmac_probe_mode,
 	.restart		= pmac_restart,
 	.power_off		= pmac_power_off,
 	.halt			= pmac_halt,

include/asm-ppc64/machdep.h

@@ -88,6 +88,7 @@ struct machdep_calls {
 
 	/* PCI stuff */
 	void		(*pcibios_fixup)(void);
+	int		(*pci_probe_mode)(struct pci_bus *);
 
 	void		(*restart)(char *cmd);
 	void		(*power_off)(void);

include/asm-ppc64/pci-bridge.h

@@ -119,5 +119,10 @@ static inline struct pci_controller *pci_bus_to_host(struct pci_bus *bus)
 	return PCI_DN(busdn)->phb;
 }
 
+/* Return values for ppc_md.pci_probe_mode function */
+#define PCI_PROBE_NONE		-1	/* Don't look at this bus at all */
+#define PCI_PROBE_NORMAL	0	/* Do normal PCI probing */
+#define PCI_PROBE_DEVTREE	1	/* Instantiate from device tree */
+
 #endif
 #endif /* __KERNEL__ */