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authorGary Hade <garyhade@us.ibm.com>2007-10-04 02:56:51 +0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-10-13 02:03:18 +0400
commit62f420f828249f686aaae949ac3439d1304a759a (patch)
tree0cc534ad4971b9155a23b46c43597d5b5dd9d548 /Documentation
parentfd64cb4606cbdd592b7119e82341d4ae5b56f2cc (diff)
downloadlinux-62f420f828249f686aaae949ac3439d1304a759a.tar.xz
PCI: use _CRS for PCI resource allocation
Use _CRS for PCI resource allocation This patch resolves an issue where incorrect PCI memory and i/o ranges are being assigned to hotplugged PCI devices on some IBM systems. The resource mis-allocation not only makes the PCI device unuseable but often makes the entire system unuseable due to resulting machine checks. The hotplug capable PCI slots on the affected systems are not located under a standard P2P bridge but are instead located under PCI root bridges or subtractive decode P2P bridges. For example, the IBM x3850 contains 2 hotplug capable PCI-X slots and 4 hotplug capable PCIe slots with the PCI-X slots each located under a PCI root bridge and the PCIe slots each located under a subtractive decode P2P bridge. The current i386/x86_64 PCI resource allocation code does not use _CRS returned resource information. No other resource information source is available for slots that are not below a standard P2P bridge so incorrect ranges are being allocated from e820 hole causing the bad result. This patch causes the kernel to use _CRS returned resource info. It is roughly based on a change provided by Matthew Wilcox for the ia64 kernel in 2005. Due to possible buggy BIOS factor and possible yet to be discovered kernel issues the function is disabled by default and can be enabled with pci=use_crs. Signed-off-by: Gary Hade <gary.hade@us.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt2
1 files changed, 2 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 3f0173f45019..e9acd5540d29 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1318,6 +1318,8 @@ and is between 256 and 4096 characters. It is defined in the file
IRQ routing is enabled.
noacpi [X86-32] Do not use ACPI for IRQ routing
or for PCI scanning.
+ use_crs [X86-32] Use _CRS for PCI resource
+ allocation.
routeirq Do IRQ routing for all PCI devices.
This is normally done in pci_enable_device(),
so this option is a temporary workaround