PCI/ACPI: Fix bus range comparison in pci_mcfg_lookup()

The configuration data provided by an MCFG entry, i.e., PCI segment and bus
range, may span multiple host bridges.

pci_mcfg_lookup() previously required an exact match of the host bridge
starting bus and the MCFG starting bus, which made the following
configuration fail:

  MCFG region:
    segment: 0
    bus range: 0x00-0xff

  host bridge
    segment: 0
    bus range: 0x20-0x4f

Relax the bus range check in pci_mcfg_lookup() so we can use any MCFG entry
that contains the required bus range, as we do in pci_mmconfig_lookup().

[bhelgaas: changelog]
Signed-off-by: Zhou Wang <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Tomasz Nowicki <[email protected]>
Acked-by: Lorenzo Pieralisi <[email protected]>

Author: Zhou Wang

drivers/acpi/pci_mcfg.c

@@ -195,11 +195,10 @@ int pci_mcfg_lookup(struct acpi_pci_root *root, struct resource *cfgres,
 		goto skip_lookup;
 
 	/*
-	 * We expect exact match, unless MCFG entry end bus covers more than
-	 * specified by caller.
+	 * We expect the range in bus_res in the coverage of MCFG bus range.
 	 */
 	list_for_each_entry(e, &pci_mcfg_list, list) {
-		if (e->segment == seg && e->bus_start == bus_res->start &&
+		if (e->segment == seg && e->bus_start <= bus_res->start &&
 		    e->bus_end >= bus_res->end) {
 			root->mcfg_addr = e->addr;
 		}