ACPI: Disable ASPM if the platform won't provide _OSC control for PCIe
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From: Jesse Barnes on 22 Jun 2010 14:40 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. -- Jesse Barnes, Intel Open Source Technology Center -- 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/ |