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PCI: Allow additional bus numbers for hotplug bridges

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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>
This commit is contained in:
Keith Busch 2016-07-21 21:40:28 -06:00 committed by Bjorn Helgaas
parent af8c34ce6a
commit e16b466059
4 changed files with 21 additions and 0 deletions
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3
Documentation/kernel-parameters.txt
View File

@ -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

8
drivers/pci/pci.c
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@ -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)) {

9
drivers/pci/probe.c
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@ -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

1
include/linux/pci.h
View File

@ -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);