summaryrefslogtreecommitdiff
path: root/drivers/pci/bus.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/pci/bus.c')
-rw-r--r--drivers/pci/bus.c70
1 files changed, 49 insertions, 21 deletions
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 5624db8c9ad0..003170ea2e39 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -64,17 +64,57 @@ void pci_bus_remove_resources(struct pci_bus *bus)
}
}
+static bool pci_bus_resource_better(struct resource *res1, bool pos1,
+ struct resource *res2, bool pos2)
+{
+ /* If exactly one is positive decode, always prefer that one */
+ if (pos1 != pos2)
+ return pos1 ? true : false;
+
+ /* Prefer the one that contains the highest address */
+ if (res1->end != res2->end)
+ return (res1->end > res2->end) ? true : false;
+
+ /* Otherwise, prefer the one with highest "center of gravity" */
+ if (res1->start != res2->start)
+ return (res1->start > res2->start) ? true : false;
+
+ /* Otherwise, choose one arbitrarily (but consistently) */
+ return (res1 > res2) ? true : false;
+}
+
+static bool pci_bus_resource_positive(struct pci_bus *bus, struct resource *res)
+{
+ struct pci_bus_resource *bus_res;
+
+ /*
+ * This relies on the fact that pci_bus.resource[] refers to P2P or
+ * CardBus bridge base/limit registers, which are always positively
+ * decoded. The pci_bus.resources list contains host bridge or
+ * subtractively decoded resources.
+ */
+ list_for_each_entry(bus_res, &bus->resources, list) {
+ if (bus_res->res == res)
+ return (bus_res->flags & PCI_SUBTRACTIVE_DECODE) ?
+ false : true;
+ }
+ return true;
+}
+
/*
- * Find the highest-address bus resource below the cursor "res". If the
- * cursor is NULL, return the highest resource.
+ * Find the next-best bus resource after the cursor "res". If the cursor is
+ * NULL, return the best resource. "Best" means that we prefer positive
+ * decode regions over subtractive decode, then those at higher addresses.
*/
static struct resource *pci_bus_find_resource_prev(struct pci_bus *bus,
unsigned int type,
struct resource *res)
{
+ bool res_pos, r_pos, prev_pos = false;
struct resource *r, *prev = NULL;
int i;
+ res_pos = pci_bus_resource_positive(bus, res);
pci_bus_for_each_resource(bus, r, i) {
if (!r)
continue;
@@ -82,26 +122,14 @@ static struct resource *pci_bus_find_resource_prev(struct pci_bus *bus,
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;
+ r_pos = pci_bus_resource_positive(bus, r);
+ if (!res || pci_bus_resource_better(res, res_pos, r, r_pos)) {
+ if (!prev || pci_bus_resource_better(r, r_pos,
+ prev, prev_pos)) {
+ prev = r;
+ prev_pos = r_pos;
+ }
}
-
- 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;