[PATCH 1/1] powerpc/64: Adjust order in pcibios_init()

[Sam Bobroff]

The pcibios_init() function for 64 bit PowerPC currently calls
pci_bus_add_devices() before pcibios_resource_survey(), which seems
incorrect because it adds devices and attempts to bind their drivers
before allocating their resources (although no problems seem to be
apparent).

So move the call to pci_bus_add_devices() to after
pcibios_resource_survey().

This will also allow the ppc_md.pcibios_bus_add_device() hooks to
perform actions that depend on PCI resources, both during rescanning
(where this is already the case) and at boot time, which should
support improvements and refactoring.

Signed-off-by: Sam Bobroff <sbobroff at linux.ibm.com>
---
Hi everyone,

I've tested this on a P9 for both the host and a KVM guest, and the change
hasn't caused any differences in PCI resource assignments or the general boot
messages.

I've also had a go at inspecting most of the code used by pci_bus_add_devices()
and pcibios_resource_survey() and it doesn't look like there are going to be
any changes in behaviour caused by reordering.  It might be worth mentioning
that the hotplug path (see pcibios_finish_adding_to_bus()) already does
resource allocation before calling pci_bus_add_devices().

However, it would be great if someone could test this change on some older
hardware or comment on wether we should make the same change on 32 bit machines.

Cheers,
Sam.

 arch/powerpc/kernel/pci_64.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index 9d8c10d55407..1ce28888dbdb 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -58,14 +58,16 @@ static int __init pcibios_init(void)
 	pci_add_flags(PCI_ENABLE_PROC_DOMAINS | PCI_COMPAT_DOMAIN_0);
 
 	/* Scan all of the recorded PCI controllers.  */
-	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
+	list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
 		pcibios_scan_phb(hose);
-		pci_bus_add_devices(hose->bus);
-	}
 
 	/* Call common code to handle resource allocation */
 	pcibios_resource_survey();
 
+	/* Add devices. */
+	list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
+		pci_bus_add_devices(hose->bus);
+
 	printk(KERN_DEBUG "PCI: Probing PCI hardware done\n");
 
 	return 0;
-- 
2.19.0.2.gcad72f5712