PCI: tegra: Implement ->{add,remove}_bus() callbacks

The configuration space mapping on Tegra is somewhat special, and in order
to avoid wasting virtual address space the configuration space for each bus
needs to be stitched together from several blocks which form a single
continuous virtual address range for accessors.

Currently the configuration space is mapped upon the first access to one of
its registers.  However, the mapping operation may sleep under certain
circumstances, so doing it from the configuration space accessors (they are
protected by a spin lock) will trigger a warning.

To avoid the warning, use the ->add_bus() callback to perform the mapping
at enumeration time when the operation is allowed to sleep.  Also add an
implementation of ->remove_bus() that undoes the mapping established by the
->add_bus() callback.  While it isn't currently possible to unload the
module, there is work underway to remedy this, and this code will come in
handy when that happens.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/host/pci-tegra.c

@@ -426,31 +426,38 @@ static struct tegra_pcie_bus *tegra_pcie_bus_alloc(struct tegra_pcie *pcie,
 	return ERR_PTR(err);
 }
 
-/*
- * Look up a virtual address mapping for the specified bus number. If no such
- * mapping exists, try to create one.
- */
-static void __iomem *tegra_pcie_bus_map(struct tegra_pcie *pcie,
-					unsigned int busnr)
+static int tegra_pcie_add_bus(struct pci_bus *bus)
 {
-	struct tegra_pcie_bus *bus;
+	struct tegra_pcie *pcie = sys_to_pcie(bus->sysdata);
+	struct tegra_pcie_bus *b;
 
-	list_for_each_entry(bus, &pcie->buses, list)
-		if (bus->nr == busnr)
-			return (void __iomem *)bus->area->addr;
+	b = tegra_pcie_bus_alloc(pcie, bus->number);
+	if (IS_ERR(b))
+		return PTR_ERR(b);
 
-	bus = tegra_pcie_bus_alloc(pcie, busnr);
-	if (IS_ERR(bus))
-		return NULL;
+	list_add_tail(&b->list, &pcie->buses);
 
-	list_add_tail(&bus->list, &pcie->buses);
+	return 0;
+}
 
-	return (void __iomem *)bus->area->addr;
+static void tegra_pcie_remove_bus(struct pci_bus *child)
+{
+	struct tegra_pcie *pcie = sys_to_pcie(child->sysdata);
+	struct tegra_pcie_bus *bus, *tmp;
+
+	list_for_each_entry_safe(bus, tmp, &pcie->buses, list) {
+		if (bus->nr == child->number) {
+			vunmap(bus->area->addr);
+			list_del(&bus->list);
+			kfree(bus);
+			break;
+		}
+	}
 }
 
-static void __iomem *tegra_pcie_conf_address(struct pci_bus *bus,
-					     unsigned int devfn,
-					     int where)
+static void __iomem *tegra_pcie_map_bus(struct pci_bus *bus,
+					unsigned int devfn,
+					int where)
 {
 	struct tegra_pcie *pcie = sys_to_pcie(bus->sysdata);
 	void __iomem *addr = NULL;
@@ -466,7 +473,12 @@ static void __iomem *tegra_pcie_conf_address(struct pci_bus *bus,
 			}
 		}
 	} else {
-		addr = tegra_pcie_bus_map(pcie, bus->number);
+		struct tegra_pcie_bus *b;
+
+		list_for_each_entry(b, &pcie->buses, list)
+			if (b->nr == bus->number)
+				addr = (void __iomem *)b->area->addr;
+
 		if (!addr) {
 			dev_err(pcie->dev,
 				"failed to map cfg. space for bus %u\n",
@@ -481,7 +493,9 @@ static void __iomem *tegra_pcie_conf_address(struct pci_bus *bus,
 }
 
 static struct pci_ops tegra_pcie_ops = {
-	.map_bus = tegra_pcie_conf_address,
+	.add_bus = tegra_pcie_add_bus,
+	.remove_bus = tegra_pcie_remove_bus,
+	.map_bus = tegra_pcie_map_bus,
 	.read = pci_generic_config_read32,
 	.write = pci_generic_config_write32,
 };