PCI: augment bus resource table with a list

Previously we used a table of size PCI_BUS_NUM_RESOURCES (16) for resources
forwarded to a bus by its upstream bridge.  We've increased this size
several times when the table overflowed.

But there's no good limit on the number of resources because host bridges
and subtractive decode bridges can forward any number of ranges to their
secondary buses.

This patch reduces the table to only PCI_BRIDGE_RESOURCE_NUM (4) entries,
which corresponds to the number of windows a PCI-to-PCI (3) or CardBus (4)
bridge can positively decode.  Any additional resources, e.g., PCI host
bridge windows or subtractively-decoded regions, are kept in a list.

I'd prefer a single list rather than this split table/list approach, but
that requires simultaneous changes to every architecture.  This approach
only requires immediate changes where we set up (a) host bridges with more
than four windows and (b) subtractive-decode P2P bridges, and we can
incrementally change other architectures to use the list.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

2 files changed, 59 insertions, 4 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index e75d219fd107..712250f5874a 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -17,6 +17,52 @@
 
 #include "pci.h"
 
+void pci_bus_add_resource(struct pci_bus *bus, struct resource *res,
+                          unsigned int flags)
+{
+        struct pci_bus_resource *bus_res;
+
+        bus_res = kzalloc(sizeof(struct pci_bus_resource), GFP_KERNEL);
+        if (!bus_res) {
+                dev_err(&bus->dev, "can't add %pR resource\n", res);
+                return;
+        }
+
+        bus_res->res = res;
+        bus_res->flags = flags;
+        list_add_tail(&bus_res->list, &bus->resources);
+}
+
+struct resource *pci_bus_resource_n(const struct pci_bus *bus, int n)
+{
+        struct pci_bus_resource *bus_res;
+
+        if (n < PCI_BRIDGE_RESOURCE_NUM)
+                return bus->resource[n];
+
+        n -= PCI_BRIDGE_RESOURCE_NUM;
+        list_for_each_entry(bus_res, &bus->resources, list) {
+                if (n-- == 0)
+                        return bus_res->res;
+        }
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(pci_bus_resource_n);
+
+void pci_bus_remove_resources(struct pci_bus *bus)
+{
+        struct pci_bus_resource *bus_res, *tmp;
+        int i;
+
+        for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++)
+                bus->resource[i] = 0;
+
+        list_for_each_entry_safe(bus_res, tmp, &bus->resources, list) {
+                list_del(&bus_res->list);
+                kfree(bus_res);
+        }
+}
+
 /**
  * pci_bus_alloc_resource - allocate a resource from a parent bus
  * @bus: PCI bus
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 70c4ed2e67cc..270d069819f7 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -89,6 +89,7 @@ static void release_pcibus_dev(struct device *dev)
 
         if (pci_bus->bridge)
                 put_device(pci_bus->bridge);
+        pci_bus_remove_resources(pci_bus);
         kfree(pci_bus);
 }
 
@@ -394,6 +395,7 @@ static void __devinit pci_read_bridge_mmio_pref(struct pci_bus *child)
 void __devinit pci_read_bridge_bases(struct pci_bus *child)
 {
         struct pci_dev *dev = child->self;
+        struct resource *res;
         int i;
 
         if (pci_is_root_bus(child))     /* It's a host bus, nothing to read */
@@ -403,17 +405,23 @@ void __devinit pci_read_bridge_bases(struct pci_bus *child)
                  child->secondary, child->subordinate,
                  dev->transparent ? " (subtractive decode)" : "");
 
+        pci_bus_remove_resources(child);
+        for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++)
+                child->resource[i] = &dev->resource[PCI_BRIDGE_RESOURCES+i];
+
         pci_read_bridge_io(child);
         pci_read_bridge_mmio(child);
         pci_read_bridge_mmio_pref(child);
 
         if (dev->transparent) {
-                for (i = 3; i < PCI_BUS_NUM_RESOURCES; i++) {
-                        child->resource[i] = child->parent->resource[i - 3];
-                        if (child->resource[i])
+                pci_bus_for_each_resource(child->parent, res, i) {
+                        if (res) {
+                                pci_bus_add_resource(child, res,
+                                                     PCI_SUBTRACTIVE_DECODE);
                                 dev_printk(KERN_DEBUG, &dev->dev,
                                            "  bridge window %pR (subtractive decode)\n",
-                                           child->resource[i]);
+                                           res);
+                        }
                 }
         }
 }
@@ -428,6 +436,7 @@ static struct pci_bus * pci_alloc_bus(void)
                 INIT_LIST_HEAD(&b->children);
                 INIT_LIST_HEAD(&b->devices);
                 INIT_LIST_HEAD(&b->slots);
+                INIT_LIST_HEAD(&b->resources);
                 b->max_bus_speed = PCI_SPEED_UNKNOWN;
                 b->cur_bus_speed = PCI_SPEED_UNKNOWN;
         }