linux-dev - Linux kernel development work

Age	Commit message (Collapse)	Author	Files	Lines
2010-12-23	PCI: Disable ASPM if BIOS asks us to	Matthew Garrett	1	-1/+4
	We currently refuse to touch the ASPM registers if the BIOS tells us that ASPM isn't supported. This can cause problems if the BIOS has (for any reason) enabled ASPM on some devices anyway. Change the code such that we explicitly clear ASPM if the FADT indicates that ASPM isn't supported, and make sure we tidy up appropriately on device removal in order to deal with the hotplug case. If ASPM is disabled because the BIOS doesn't hand over control then we won't touch the registers. Signed-off-by: Matthew Garrett <mjg@redhat.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
2008-07-28	PCI: disable ASPM per ACPI FADT setting	Shaohua Li	1	-0/+5
	The ACPI FADT table includes an ASPM control bit. If the bit is set, do not enable ASPM since it may indicate that the platform doesn't actually support the feature. Tested-by: Jack Howarth <howarth@bromo.msbb.uc.edu> Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
2008-04-20	PCI: add PCI Express ASPM support	Shaohua Li	1	-0/+56
	PCI Express ASPM defines a protocol for PCI Express components in the D0 state to reduce Link power by placing their Links into a low power state and instructing the other end of the Link to do likewise. This capability allows hardware-autonomous, dynamic Link power reduction beyond what is achievable by software-only controlled power management. However, The device should be configured by software appropriately. Enabling ASPM will save power, but will introduce device latency. This patch adds ASPM support in Linux. It introduces a global policy for ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control it. The interface can be used as a boot option too. Currently we have below setting: -default, BIOS default setting -powersave, highest power saving mode, enable all available ASPM state and clock power management -performance, highest performance, disable ASPM and clock power management By default, the 'default' policy is used currently. In my test, power difference between powersave mode and performance mode is about 1.3w in a system with 3 PCIE links. Note: some devices might not work well with aspm, either because chipset issue or device issue. The patch provide API (pci_disable_link_state), driver can disable ASPM for specific device. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>