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Commit e16b4660 authored by Keith Busch's avatar Keith Busch Committed by Bjorn Helgaas
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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: default avatarKeith Busch <keith.busch@intel.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent af8c34ce

Documentation/kernel-parameters.txt

+3 −0
Original line number Diff line number Diff line
@@ -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

drivers/pci/pci.c

+8 −0
Original line number Diff line number Diff line
@@ -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)) {

drivers/pci/probe.c

+9 −0
Original line number Diff line number Diff line
@@ -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

include/linux/pci.h

+1 −0
Original line number Diff line number Diff line
@@ -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);