PCI: Revert early bridge resource set up

The commit a43ac32 ("PCI: Set up bridge resources earlier") moved
bridge window resources set up earlier than before. The change was
necessary to support another change that got pulled on the last minute
due to breaking s390 and other systems.

The presence of valid bridge window resources earlier than before allows
pci_assign_unassigned_root_bus_resources() call from pci_host_probe()
assign the bridge windows. Some host bridges, however, have to wait first
for the link up event before they can enumerate successfully (see e.g.
qcom_pcie_global_irq_thread()) and thus the bus has not been enumerated yet
while calling pci_host_probe().

Calling pci_assign_unassigned_root_bus_resources() without results from
enumeration can result in sizing bridge windows with too small sizes which
cannot be later corrected after the enumeration has completed because
bridge windows have become pinned in place by the other resources.

Interestingly, it seems pci_read_bridge_bases() is not called at all in the
problematic case and the bridge window resource type setup is done by
pci_bridge_check_ranges() and sizing by the usual resource fitting logic.

The root problem behind all this looks pretty generic. If resource fitting
is called too early, the hotplug reservation and old size lower bounding
cause the bridge windows to be assigned without children but with non-zero
size, which leads to these pinning problems. As such, this can likely be
solved on the general level but the solution does not look trivial.

As the commit a43ac32 ("PCI: Set up bridge resources earlier") was
prequisite for other change that did not end up into kernel yet, revert it
to resolve the resource assignment failures and give time to code and test
a generic solution.

Fixes: a43ac32 ("PCI: Set up bridge resources earlier")
Reported-by: Val Packett <val@packett.cool>
Link: https://lore.kernel.org/r/017ff8df-511c-4da8-b3cf-edf2cb7f1a67@packett.cool
Reported-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/df266709-a9b3-4fd8-af3a-c22eb3c9523a@roeck-us.net
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251014163602.17138-1-ilpo.jarvinen@linux.intel.com

Author: ij-intel

drivers/pci/probe.c

@@ -538,14 +538,10 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
 	}
 	if (io) {
 		bridge->io_window = 1;
-		pci_read_bridge_io(bridge,
-				   pci_resource_n(bridge, PCI_BRIDGE_IO_WINDOW),
-				   true);
+		pci_read_bridge_io(bridge, &res, true);
 	}
 
-	pci_read_bridge_mmio(bridge,
-			     pci_resource_n(bridge, PCI_BRIDGE_MEM_WINDOW),
-			     true);
+	pci_read_bridge_mmio(bridge, &res, true);
 
 	/*
 	 * DECchip 21050 pass 2 errata: the bridge may miss an address
@@ -583,10 +579,7 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
 			bridge->pref_64_window = 1;
 	}
 
-	pci_read_bridge_mmio_pref(bridge,
-				  pci_resource_n(bridge,
-						 PCI_BRIDGE_PREF_MEM_WINDOW),
-				  true);
+	pci_read_bridge_mmio_pref(bridge, &res, true);
 }
 
 void pci_read_bridge_bases(struct pci_bus *child)