| From: Matthew Garrett <mjg@redhat.com> |
| Subject: ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe |
| |
| 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. |
| |
| Signed-off-by: Matthew Garrett <mjg@redhat.com> |
| |
| |
| diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c |
| index 4eac593..1f67057 100644 |
| |
| |
| @@ -33,6 +33,7 @@ |
| #include <linux/pm_runtime.h> |
| #include <linux/pci.h> |
| #include <linux/pci-acpi.h> |
| +#include <linux/pci-aspm.h> |
| #include <linux/acpi.h> |
| #include <linux/slab.h> |
| #include <acpi/acpi_bus.h> |
| @@ -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, |
| + 0); |
| + |
| + if (status == AE_NOT_EXIST) { |
| + 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); |