From 852972acff8f10f3a15679be2059bb94916cba5d Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Tue, 22 Jun 2010 11:25:43 -0400 Subject: [PATCH] ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe The PCI SIG documentation for the _OSC OS/firmware handshaking interface states: "If the _OSC control method is absent from the scope of a host bridge device, then the operating system must not enable or attempt to use any features defined in this section for the hierarchy originated by the host bridge." The obvious interpretation of this is that the OS should not attempt to use PCIe hotplug, PME or AER - however, the specification also notes that an _OSC method is *required* for PCIe hierarchies, and experimental validation with An Alternative OS indicates that it doesn't use any PCIe functionality if the _OSC method is missing. That arguably means we shouldn't be using MSI or extended config space, but right now our problems seem to be limited to vendors being surprised when ASPM gets enabled on machines when other OSs refuse to do so. So, for now, let's just disable ASPM if the _OSC method doesn't exist or refuses to hand over PCIe capability control. Acked-by: Rafael J. Wysocki Signed-off-by: Matthew Garrett Signed-off-by: Jesse Barnes --- drivers/acpi/pci_root.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c index 4eac59393edc..1f67057af2a5 100644 --- a/drivers/acpi/pci_root.c +++ b/drivers/acpi/pci_root.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include #include @@ -543,6 +544,14 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device) if (flags != base_flags) acpi_pci_osc_support(root, flags); + status = acpi_pci_osc_control_set(root->device->handle, + OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL); + + if (ACPI_FAILURE(status)) { + printk(KERN_INFO "Unable to assume PCIe control: Disabling ASPM\n"); + pcie_no_aspm(); + } + pci_acpi_add_bus_pm_notifier(device, root->bus); if (device->wakeup.flags.run_wake) device_set_run_wake(root->bus->bridge, true); -- 2.20.1