From 6cac12dfab9c57a4f76821412224b226a9b08dff Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 10 Nov 2011 16:38:33 -0500 Subject: PCI: Rework ASPM disable code commit 3c076351c4027a56d5005a39a0b518a4ba393ce2 upstream. Right now we forcibly clear ASPM state on all devices if the BIOS indicates that the feature isn't supported. Based on the Microsoft presentation "PCI Express In Depth for Windows Vista and Beyond", I'm starting to think that this may be an error. The implication is that unless the platform grants full control via _OSC, Windows will not touch any PCIe features - including ASPM. In that case clearing ASPM state would be an error unless the platform has granted us that control. This patch reworks the ASPM disabling code such that the actual clearing of state is triggered by a successful handoff of PCIe control to the OS. The general ASPM code undergoes some changes in order to ensure that the ability to clear the bits isn't overridden by ASPM having already been disabled. Further, this theoretically now allows for situations where only a subset of PCIe roots hand over control, leaving the others in the BIOS state. It's difficult to know for sure that this is the right thing to do - there's zero public documentation on the interaction between all of these components. But enough vendors enable ASPM on platforms and then set this bit that it seems likely that they're expecting the OS to leave them alone. Measured to save around 5W on an idle Thinkpad X220. Signed-off-by: Matthew Garrett Signed-off-by: Jesse Barnes Signed-off-by: Greg Kroah-Hartman --- include/linux/pci-aspm.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h index 7cea7b6c141..c8320144fe7 100644 --- a/include/linux/pci-aspm.h +++ b/include/linux/pci-aspm.h @@ -29,7 +29,7 @@ extern void pcie_aspm_pm_state_change(struct pci_dev *pdev); extern void pcie_aspm_powersave_config_link(struct pci_dev *pdev); extern void pci_disable_link_state(struct pci_dev *pdev, int state); extern void pci_disable_link_state_locked(struct pci_dev *pdev, int state); -extern void pcie_clear_aspm(void); +extern void pcie_clear_aspm(struct pci_bus *bus); extern void pcie_no_aspm(void); #else static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) @@ -47,7 +47,7 @@ static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) static inline void pci_disable_link_state(struct pci_dev *pdev, int state) { } -static inline void pcie_clear_aspm(void) +static inline void pcie_clear_aspm(struct pci_bus *bus) { } static inline void pcie_no_aspm(void) -- cgit v1.2.3-18-g5258