1 files changed, 48 insertions, 5 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 7f0af0e9b826..172bf26e0680 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -64,6 +64,49 @@ void pci_bus_remove_resources(struct pci_bus *bus)
         }
 }
 
+/*
+ * Find the highest-address bus resource below the cursor "res".  If the
+ * cursor is NULL, return the highest resource.
+ */
+static struct resource *pci_bus_find_resource_prev(struct pci_bus *bus,
+                                                   unsigned int type,
+                                                   struct resource *res)
+{
+        struct resource *r, *prev = NULL;
+        int i;
+
+        pci_bus_for_each_resource(bus, r, i) {
+                if (!r)
+                        continue;
+
+                if ((r->flags & IORESOURCE_TYPE_BITS) != type)
+                        continue;
+
+                /* If this resource is at or past the cursor, skip it */
+                if (res) {
+                        if (r == res)
+                                continue;
+                        if (r->end > res->end)
+                                continue;
+                        if (r->end == res->end && r->start > res->start)
+                                continue;
+                }
+
+                if (!prev)
+                        prev = r;
+
+                /*
+                 * A small resource is higher than a large one that ends at
+                 * the same address.
+                 */
+                if (r->end > prev->end ||
+                    (r->end == prev->end && r->start > prev->start))
+                        prev = r;
+        }
+
+        return prev;
+}
+
 /**
  * pci_bus_alloc_resource - allocate a resource from a parent bus
  * @bus: PCI bus
@@ -89,9 +132,10 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
                                           resource_size_t),
                 void *alignf_data)
 {
-        int i, ret = -ENOMEM;
+        int ret = -ENOMEM;
         struct resource *r;
         resource_size_t max = -1;
+        unsigned int type = res->flags & IORESOURCE_TYPE_BITS;
 
         type_mask |= IORESOURCE_IO | IORESOURCE_MEM;
 
@@ -99,10 +143,9 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
         if (!(res->flags & IORESOURCE_MEM_64))
                 max = PCIBIOS_MAX_MEM_32;
 
-        pci_bus_for_each_resource(bus, r, i) {
-                if (!r)
-                        continue;
-
+        /* Look for space at highest addresses first */
+        r = pci_bus_find_resource_prev(bus, type, NULL);
+        for ( ; r; r = pci_bus_find_resource_prev(bus, type, r)) {
                 /* type_mask must match */
                 if ((res->flags ^ r->flags) & type_mask)
                         continue;