PCI: get larger bridge ranges when space is available

Found one system:
[   71.120590] pci 0000:40:05.0: scanning behind bridge, config 4f4a40, pass 0
[   71.138283] PCI: Scanning bus 0000:4a
[   71.140341] pci 0000:4a:00.0: found [15b3:6278] class 000c06 header type 00
[   71.157173] pci 0000:4a:00.0: reg 10 64bit mmio: [0x000000-0x0fffff]
[   71.161697] pci 0000:4a:00.0: reg 18 64bit mmio pref: [0x000000-0x7fffff]
[   71.179403] pci 0000:4a:00.0: reg 20 64bit mmio pref: [0x000000-0xfffffff]
[   71.185366] pci 0000:4a:00.0: calling quirk_resource_alignment+0x0/0x1dd
[   71.200846] pci 0000:4a:00.0: disabling ASPM on pre-1.1 PCIe device.  You can enable it with 'pcie_aspm=force'
[   71.219623] PCI: Fixups for bus 0000:4a
[   71.222194] pci 0000:40:05.0: bridge 32bit mmio: [0xcf000000-0xcf0fffff]
[   71.238662] pci 0000:40:05.0: bridge 64bit mmio pref: [0xcd800000-0xcdffffff]
[   71.255793] PCI: Bus scan for 0000:4a returning with max=4a

Device needs a big pref mmio, but BIOS doesn't allocate mmio to it aside
from a small MMIO range.  Later, the kernel will not allocate resources to
that to the device:
[   99.574030] pci 0000:4a:00.0: BAR 4: can't allocate mem resource [0xd0000000-0xcdffffff]
[   99.580102] pci 0000:4a:00.0: BAR 2: got res [0xcd800000-0xcdffffff] bus [0xcd800000-0xcdffffff] flags 0x12120c
[   99.602307] pci 0000:4a:00.0: BAR 2: moved to bus [0xcd800000-0xcdffffff] flags 0x12120c
[   99.615991] pci 0000:4a:00.0: BAR 0: got res [0xcf000000-0xcf0fffff] bus [0xcf000000-0xcf0fffff] flags 0x120204
[   99.634499] pci 0000:4a:00.0: BAR 0: moved to bus [0xcf000000-0xcf0fffff] flags 0x120204
[   99.654318] pci 0000:40:05.0: PCI bridge, secondary bus 0000:4a
[   99.658766] pci 0000:40:05.0:   IO window: disabled
[   99.675478] pci 0000:40:05.0:   MEM window: 0xcf000000-0xcf0fffff
[   99.681663] pci 0000:40:05.0:   PREFETCH window: 0x000000cd800000-0x000000cdffffff

So try to get a big range in the pci bridge if there is no child using
that range.  With the patch we get:
[   99.104525] pci 0000:4a:00.0: BAR 4: got res [0xfc080000000-0xfc08fffffff] bus [0xfc080000000-0xfc08fffffff] flags 0x12120c
[   99.123624] pci 0000:4a:00.0: BAR 4: moved to bus [0xfc080000000-0xfc08fffffff] flags 0x12120c
[   99.131977] pci 0000:4a:00.0: BAR 2: got res [0xfc090000000-0xfc0907fffff] bus [0xfc090000000-0xfc0907fffff] flags 0x12120c
[   99.149788] pci 0000:4a:00.0: BAR 2: moved to bus [0xfc090000000-0xfc0907fffff] flags 0x12120c
[   99.169248] pci 0000:4a:00.0: BAR 0: got res [0xc0200000-0xc02fffff] bus [0xc0200000-0xc02fffff] flags 0x120204
[   99.189508] pci 0000:4a:00.0: BAR 0: moved to bus [0xc0200000-0xc02fffff] flags 0x120204
[   99.206402] pci 0000:40:05.0: PCI bridge, secondary bus 0000:4a
[   99.210637] pci 0000:40:05.0:   IO window: disabled
[   99.224856] pci 0000:40:05.0:   MEM window: 0xc0200000-0xc03fffff
[   99.230019] pci 0000:40:05.0:   PREFETCH window: 0x000fc080000000-0x000fc097ffffff
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/setup-bus.c

@@ -299,8 +299,17 @@ static struct resource *find_free_bus_resource(struct pci_bus *bus, unsigned lon
 		r = bus->resource[i];
 		if (r == &ioport_resource || r == &iomem_resource)
 			continue;
-		if (r && (r->flags & type_mask) == type && !r->parent)
-			return r;
+		if (r && (r->flags & type_mask) == type) {
+			if (!r->parent)
+				return r;
+			/*
+			 * if there is no child under that, we should release
+			 * and use it. don't need to reset it, pbus_size_* will
+			 * set it again
+			 */
+			if (!r->child && !release_resource(r))
+				return r;
+		}
 	}
 	return NULL;
 }