x86/PCI: coalesce overlapping host bridge windows

Some BIOSes provide PCI host bridge windows that overlap, e.g.,

    pci_root PNP0A03:00: host bridge window [mem 0xb0000000-0xffffffff]
    pci_root PNP0A03:00: host bridge window [mem 0xafffffff-0xdfffffff]
    pci_root PNP0A03:00: host bridge window [mem 0xf0000000-0xffffffff]

If we simply insert these as children of iomem_resource, the second window
fails because it conflicts with the first, and the third is inserted as a
child of the first, i.e.,

    b0000000-ffffffff PCI Bus 0000:00
      f0000000-ffffffff PCI Bus 0000:00

When we claim PCI device resources, this can cause collisions like this
if we put them in the first window:

    pci 0000:00:01.0: address space collision: [mem 0xff300000-0xff4fffff] conflicts with PCI Bus 0000:00 [mem 0xf0000000-0xffffffff]

Host bridge windows are top-level resources by definition, so it doesn't
make sense to make the third window a child of the first.  This patch
coalesces any host bridge windows that overlap.  For the example above,
the result is this single window:

    pci_root PNP0A03:00: host bridge window [mem 0xafffffff-0xffffffff]

This fixes a 2.6.34 regression.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=17011
Reported-and-tested-by: Anisse Astier <anisse@astier.eu>
Reported-and-tested-by: Pramod Dematagoda <pmd.lotr.gandalf@gmail.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

arch/x86/pci/acpi.c

@@ -138,7 +138,6 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
 	struct acpi_resource_address64 addr;
 	acpi_status status;
 	unsigned long flags;
-	struct resource *root, *conflict;
 	u64 start, end;
 
 	status = resource_to_addr(acpi_res, &addr);
@@ -146,12 +145,10 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
 		return AE_OK;
 
 	if (addr.resource_type == ACPI_MEMORY_RANGE) {
-		root = &iomem_resource;
 		flags = IORESOURCE_MEM;
 		if (addr.info.mem.caching == ACPI_PREFETCHABLE_MEMORY)
 			flags |= IORESOURCE_PREFETCH;
 	} else if (addr.resource_type == ACPI_IO_RANGE) {
-		root = &ioport_resource;
 		flags = IORESOURCE_IO;
 	} else
 		return AE_OK;
@@ -172,25 +169,90 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
 		return AE_OK;
 	}
 
-	conflict = insert_resource_conflict(root, res);
-	if (conflict) {
-		dev_err(&info->bridge->dev,
-			"address space collision: host bridge window %pR "
-			"conflicts with %s %pR\n",
-			res, conflict->name, conflict);
-	} else {
-		pci_bus_add_resource(info->bus, res, 0);
-		info->res_num++;
-		if (addr.translation_offset)
-			dev_info(&info->bridge->dev, "host bridge window %pR "
-				 "(PCI address [%#llx-%#llx])\n",
-				 res, res->start - addr.translation_offset,
-				 res->end - addr.translation_offset);
+	info->res_num++;
+	if (addr.translation_offset)
+		dev_info(&info->bridge->dev, "host bridge window %pR "
+			 "(PCI address [%#llx-%#llx])\n",
+			 res, res->start - addr.translation_offset,
+			 res->end - addr.translation_offset);
+	else
+		dev_info(&info->bridge->dev, "host bridge window %pR\n", res);
+
+	return AE_OK;
+}
+
+static bool resource_contains(struct resource *res, resource_size_t point)
+{
+	if (res->start <= point && point <= res->end)
+		return true;
+	return false;
+}
+
+static void coalesce_windows(struct pci_root_info *info, int type)
+{
+	int i, j;
+	struct resource *res1, *res2;
+
+	for (i = 0; i < info->res_num; i++) {
+		res1 = &info->res[i];
+		if (!(res1->flags & type))
+			continue;
+
+		for (j = i + 1; j < info->res_num; j++) {
+			res2 = &info->res[j];
+			if (!(res2->flags & type))
+				continue;
+
+			/*
+			 * I don't like throwing away windows because then
+			 * our resources no longer match the ACPI _CRS, but
+			 * the kernel resource tree doesn't allow overlaps.
+			 */
+			if (resource_contains(res1, res2->start) ||
+			    resource_contains(res1, res2->end) ||
+			    resource_contains(res2, res1->start) ||
+			    resource_contains(res2, res1->end)) {
+				res1->start = min(res1->start, res2->start);
+				res1->end = max(res1->end, res2->end);
+				dev_info(&info->bridge->dev,
+					 "host bridge window expanded to %pR; %pR ignored\n",
+					 res1, res2);
+				res2->flags = 0;
+			}
+		}
+	}
+}
+
+static void add_resources(struct pci_root_info *info)
+{
+	int i;
+	struct resource *res, *root, *conflict;
+
+	if (!pci_use_crs)
+		return;
+
+	coalesce_windows(info, IORESOURCE_MEM);
+	coalesce_windows(info, IORESOURCE_IO);
+
+	for (i = 0; i < info->res_num; i++) {
+		res = &info->res[i];
+
+		if (res->flags & IORESOURCE_MEM)
+			root = &iomem_resource;
+		else if (res->flags & IORESOURCE_IO)
+			root = &ioport_resource;
 		else
-			dev_info(&info->bridge->dev,
-				 "host bridge window %pR\n", res);
+			continue;
+
+		conflict = insert_resource_conflict(root, res);
+		if (conflict)
+			dev_err(&info->bridge->dev,
+				"address space collision: host bridge window %pR "
+				"conflicts with %s %pR\n",
+				res, conflict->name, conflict);
+		else
+			pci_bus_add_resource(info->bus, res, 0);
 	}
-	return AE_OK;
 }
 
 static void
@@ -224,6 +286,7 @@ get_current_resources(struct acpi_device *device, int busnum,
 	acpi_walk_resources(device->handle, METHOD_NAME__CRS, setup_resource,
 				&info);
 
+	add_resources(&info);
 	return;
 
 name_alloc_fail: