Why check for PCI_PROBE_ONLY in pci_common_init_dev()

* Why check for PCI_PROBE_ONLY in pci_common_init_dev()
@ 2019-06-13  3:52 Benjamin Herrenschmidt
  2019-06-13 22:06 ` Russell King - ARM Linux admin
  0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Herrenschmidt @ 2019-06-13  3:52 UTC (permalink / raw)
  To: linux-arm-kernel; +Cc: Lorenzo Pieralisi

Hi !

So while trying to sort out & cleanup the business with PCI resource
allocation (and do the ground work to be able to revive 
https://lore.kernel.org/linux-pci/20150916085850.GA17510@red-moon/) I
stumbled upon this one:

arch/arm/kernel/bios32.c:pci_common_init_dev() checks for
PCI_PROBE_ONLY to decide whether to claim existing resources or
reallocate.

However, I can't see any code path leading to that function that would
have set that flag.

IE. Afaik, PCI_PROBE_ONLY is only set in a limited number of places
(short of a grep failure on my part):

arch/alpha/kernel/sys_marvel.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/alpha/kernel/sys_titan.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-bcm1480.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-sb1250.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-virtio-guest.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-xlp.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-xlr.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/mips/pci/pci-xtalk-bridge.c:	pci_set_flags(PCI_PROBE_ONLY);
arch/powerpc/platforms/maple/pci.c:	pci_add_flags(PCI_PROBE_ONLY);
arch/powerpc/platforms/pseries/setup.c:	pci_add_flags(PCI_PROBE_ONLY);
drivers/pci/of.c:		pci_add_flags(PCI_PROBE_ONLY);

The only one being of interest to arm32 here being the last one in
of_pci_check_probe_only().

Now that function is only called in two places:

arch/powerpc/platforms/pseries/setup.c: of_pci_check_probe_only();
drivers/pci/controller/pci-host-common.c:       of_pci_check_probe_only();

The only interesting call site here being pci-host-common.c, which
corresponds to the "new style" platform device based PCI host bridge
probing. Now those use pci_host_probe() in drivers/pci/probe.c, not the 
(legacy ?) arch/arm/kernel/bios32.c variant.

So unless I missed something, should I take out the PCI_PROBE_ONLY
case completely in the arm32 code as part of my series ?

ie:

index ed46ca69813d..f969a1a56ace 100644

--- a/arch/arm/kernel/bios32.c
+++ b/arch/arm/kernel/bios32.c
@@ -536,23 +536,13 @@ void pci_common_init_dev(struct device *parent, struct hw_pci *hw)
 
 	list_for_each_entry(sys, &head, node) {
 		struct pci_bus *bus = sys->bus;
+		struct pci_bus *child;
 
-		/*
-		 * We insert PCI resources into the iomem_resource and
-		 * ioport_resource trees in either pci_bus_claim_resources()
-		 * or pci_bus_assign_resources().
-		 */
-		if (pci_has_flag(PCI_PROBE_ONLY)) {
-			pci_bus_claim_resources(bus);
-		} else {
-			struct pci_bus *child;
+		pci_bus_size_bridges(bus);
+		pci_bus_assign_resources(bus);
 
-			pci_bus_size_bridges(bus);
-			pci_bus_assign_resources(bus);
-
-			list_for_each_entry(child, &bus->children, node)
-				pcie_bus_configure_settings(child);
-		}
+		list_for_each_entry(child, &bus->children, node)
+			pcie_bus_configure_settings(child);
 
 		pci_bus_add_devices(bus);
 	}

Cheers,
Ben.



_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 3+ messages in thread