linux-kernel - Re: [PATCH] ACPI: Disable ASPM if the platform won't provide

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Message-ID: <20100622112908.4122ceb2@virtuousgeek.org>
Date:	Tue, 22 Jun 2010 11:29:08 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Matthew Garrett <mjg@...hat.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: Disable ASPM if the platform won't provide _OSC
 control for PCIe

On Tue, 22 Jun 2010 20:17:29 +0200
"Rafael J. Wysocki" <rjw@...k.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@...hat.com>
> 
> Acked-by: Rafael J. Wysocki <rjw@...k.pl>

Applied to my linux-next branch, thanks.

-- 
Jesse Barnes, Intel Open Source Technology Center
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