2 files changed, 103 insertions, 0 deletions

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 1dc8a8066761..cbd40f05c39c 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -385,6 +385,8 @@ static inline int pci_resource_num(const struct pci_dev *dev,
 	return resno;
 }
 
+struct resource *pbus_select_window(struct pci_bus *bus,
+				    const struct resource *res);
 void pci_reassigndev_resource_alignment(struct pci_dev *dev);
 void pci_disable_bridge_window(struct pci_dev *dev);
 struct pci_bus *pci_bus_get(struct pci_bus *bus);
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 70b210ed200d..913fd41e1d0d 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -172,6 +172,107 @@ static struct resource *find_bus_resource_of_type(struct pci_bus *bus,
 	return r_assigned;
 }
 
+/**
+ * pbus_select_window_for_type - Select bridge window for a resource type
+ * @bus: PCI bus
+ * @type: Resource type (resource flags can be passed as is)
+ *
+ * Select the bridge window based on a resource @type.
+ *
+ * For memory resources, the selection is done as follows:
+ *
+ * Any non-prefetchable resource is put into the non-prefetchable window.
+ *
+ * If there is no prefetchable MMIO window, put all memory resources into the
+ * non-prefetchable window.
+ *
+ * If there's a 64-bit prefetchable MMIO window, put all 64-bit prefetchable
+ * resources into it and place 32-bit prefetchable memory into the
+ * non-prefetchable window.
+ *
+ * Otherwise, put all prefetchable resources into the prefetchable window.
+ *
+ * Return: the bridge window resource or NULL if no bridge window is found.
+ */
+static struct resource *pbus_select_window_for_type(struct pci_bus *bus,
+						    unsigned long type)
+{
+	int iores_type = type & IORESOURCE_TYPE_BITS;	/* w/o 64bit & pref */
+	struct resource *mmio, *mmio_pref, *win;
+
+	type &= PCI_RES_TYPE_MASK;			/* with 64bit & pref */
+
+	if ((iores_type != IORESOURCE_IO) && (iores_type != IORESOURCE_MEM))
+		return NULL;
+
+	if (pci_is_root_bus(bus)) {
+		win = find_bus_resource_of_type(bus, type, type);
+		if (win)
+			return win;
+
+		type &= ~IORESOURCE_MEM_64;
+		win = find_bus_resource_of_type(bus, type, type);
+		if (win)
+			return win;
+
+		type &= ~IORESOURCE_PREFETCH;
+		return find_bus_resource_of_type(bus, type, type);
+	}
+
+	switch (iores_type) {
+	case IORESOURCE_IO:
+		return pci_bus_resource_n(bus, PCI_BUS_BRIDGE_IO_WINDOW);
+
+	case IORESOURCE_MEM:
+		mmio = pci_bus_resource_n(bus, PCI_BUS_BRIDGE_MEM_WINDOW);
+		mmio_pref = pci_bus_resource_n(bus, PCI_BUS_BRIDGE_PREF_MEM_WINDOW);
+
+		if (!(type & IORESOURCE_PREFETCH) ||
+		    !(mmio_pref->flags & IORESOURCE_MEM))
+			return mmio;
+
+		if ((type & IORESOURCE_MEM_64) ||
+		    !(mmio_pref->flags & IORESOURCE_MEM_64))
+			return mmio_pref;
+
+		return mmio;
+	default:
+		return NULL;
+	}
+}
+
+/**
+ * pbus_select_window - Select bridge window for a resource
+ * @bus: PCI bus
+ * @res: Resource
+ *
+ * Select the bridge window for @res. If the resource is already assigned,
+ * return the current bridge window.
+ *
+ * For memory resources, the selection is done as follows:
+ *
+ * Any non-prefetchable resource is put into the non-prefetchable window.
+ *
+ * If there is no prefetchable MMIO window, put all memory resources into the
+ * non-prefetchable window.
+ *
+ * If there's a 64-bit prefetchable MMIO window, put all 64-bit prefetchable
+ * resources into it and place 32-bit prefetchable memory into the
+ * non-prefetchable window.
+ *
+ * Otherwise, put all prefetchable resources into the prefetchable window.
+ *
+ * Return: the bridge window resource or NULL if no bridge window is found.
+ */
+struct resource *pbus_select_window(struct pci_bus *bus,
+				    const struct resource *res)
+{
+	if (res->parent)
+		return res->parent;
+
+	return pbus_select_window_for_type(bus, res->flags);
+}
+
 static bool pdev_resources_assignable(struct pci_dev *dev)
 {
 	u16 class = dev->class >> 8, command;