ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe
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From: Rafael J. Wysocki on 22 Jun 2010 14:20 On Tuesday, June 22, 2010, Matthew Garrett wrote: > 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(a)redhat.com> Acked-by: Rafael J. Wysocki <rjw(a)sisk.pl> > --- > drivers/acpi/pci_root.c | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c > index 1af8081..7167213 100644 > --- a/drivers/acpi/pci_root.c > +++ b/drivers/acpi/pci_root.c > @@ -32,6 +32,7 @@ > #include <linux/pm.h> > #include <linux/pci.h> > #include <linux/pci-acpi.h> > +#include <linux/pci-aspm.h> > #include <linux/acpi.h> > #include <acpi/acpi_bus.h> > #include <acpi/acpi_drivers.h> > @@ -576,6 +577,14 @@ 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(); > + } > + > return 0; > > end: > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Rafael J. Wysocki on 22 Jun 2010 14:50
On Tuesday, June 22, 2010, Jesse Barnes wrote: > On Tue, 22 Jun 2010 20:17:29 +0200 > "Rafael J. Wysocki" <rjw(a)sisk.pl> wrote: > > > On Tuesday, June 22, 2010, Matthew Garrett wrote: > > > 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(a)redhat.com> > > > > Acked-by: Rafael J. Wysocki <rjw(a)sisk.pl> > > Applied to my linux-next branch, thanks. I think it's 2.6.35 (and probably -stable) material, these problems aleady happen in the field. Matthew, what do you think? Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |