PCI: Allow additional bus numbers for hotplug bridges

A user may hot add a switch requiring more than one bus to enumerate.  This
previously required a system reboot if BIOS did not sufficiently pad the
bus resource, which they frequently don't do.

Add a kernel parameter so a user can specify the minimum number of bus
numbers to reserve for a hotplug bridge's subordinate buses so rebooting
won't be necessary.

The default is 1, which is equivalent to previous behavior.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c958d1c7def4eac5c9931a0e8a6f9aab6c6..487e799b1da21900a960f9a3e409157a412cbda9 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3016,6 +3016,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                hpmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for hotplug bridge's memory window.
                                Default size is 2 megabytes.
+               hpbussize=nn    The minimum amount of additional bus numbers
+                               reserved for buses below a hotplug bridge.
+                               Default is 1.
                realloc=        Enable/disable reallocating PCI bridge resources
                                if allocations done by BIOS are too small to
                                accommodate resources required by all child

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index c8b4dbdd1bddae95c214e92b52492b82364afcaf..f18ea90cf91a4477483c5c94f8fa36c9bb3780eb 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -81,6 +81,9 @@ unsigned long pci_cardbus_mem_size = DEFAULT_CARDBUS_MEM_SIZE;
 unsigned long pci_hotplug_io_size  = DEFAULT_HOTPLUG_IO_SIZE;
 unsigned long pci_hotplug_mem_size = DEFAULT_HOTPLUG_MEM_SIZE;
 
+#define DEFAULT_HOTPLUG_BUS_SIZE       1
+unsigned long pci_hotplug_bus_size = DEFAULT_HOTPLUG_BUS_SIZE;
+
 enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT;
 
 /*
@@ -5021,6 +5024,11 @@ static int __init pci_setup(char *str)
                                pci_hotplug_io_size = memparse(str + 9, &str);
                        } else if (!strncmp(str, "hpmemsize=", 10)) {
                                pci_hotplug_mem_size = memparse(str + 10, &str);
+                       } else if (!strncmp(str, "hpbussize=", 10)) {
+                               pci_hotplug_bus_size =
+                                       simple_strtoul(str + 10, &str, 0);
+                               if (pci_hotplug_bus_size > 0xff)
+                                       pci_hotplug_bus_size = DEFAULT_HOTPLUG_BUS_SIZE;
                        } else if (!strncmp(str, "pcie_bus_tune_off", 17)) {
                                pcie_bus_config = PCIE_BUS_TUNE_OFF;
                        } else if (!strncmp(str, "pcie_bus_safe", 13)) {

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8e3ef720997dfba2858c4dae77b2a0651f678c2d..f680099c110da3fc11ae1f0ef5c597adfba401e4 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2076,6 +2076,15 @@ unsigned int pci_scan_child_bus(struct pci_bus *bus)
                                max = pci_scan_bridge(bus, dev, max, pass);
                }
 
+       /*
+        * Make sure a hotplug bridge has at least the minimum requested
+        * number of buses.
+        */
+       if (bus->self && bus->self->is_hotplug_bridge && pci_hotplug_bus_size) {
+               if (max - bus->busn_res.start < pci_hotplug_bus_size - 1)
+                       max = bus->busn_res.start + pci_hotplug_bus_size - 1;
+       }
+
        /*
         * We've scanned the bus and so we know all about what's on
         * the other side of any bridges that may be on this bus plus

diff --git a/include/linux/pci.h b/include/linux/pci.h
index b67e4df2080130b75b8c925921fa5f13e464496c..0c283254111d87c8e44b27e8d4c101493b8c98b5 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1706,6 +1706,7 @@ extern u8 pci_cache_line_size;
 
 extern unsigned long pci_hotplug_io_size;
 extern unsigned long pci_hotplug_mem_size;
+extern unsigned long pci_hotplug_bus_size;
 
 /* Architecture-specific versions may override these (weak) */
 void pcibios_disable_device(struct pci_dev *dev);