ASPM enabled by default - mild potential for breakage

[Matthew Garrett]

On Thu, Jul 16, 2009 at 09:49:56PM -0700, Arjan van de Ven wrote:
> On Thu, 16 Jul 2009 22:28:57 +0100
> Matthew Garrett <mjg at redhat.com> wrote:
> 
> > I've just flicked ASPM (Active State Power Management - runtime power 
> > saving on PCIe hardware) on by default, and it'll be that way in the 
> > next rawhide kernel build. There's the potential for some buggy
> > hardware to be upset by this. If your system no longer boots or some
> > hardware doesn't work, try booting with the
> > 
> 
> are you sure you want to do this?
> the bios is supposed to set this up already...

"supposed to"? Spec doesn't require it. If the BIOS flags it as being 
unsupported then we won't enable it.

> ... except on chipsets where there's known hw issues (first
> generations) .... (including ICH7's etc)
> 
> so enabling it by force is maybe not always a good idea.

We're using the same heuristics as Microsoft here - don't use it if the 
FADT asks us not to, and don't use it if the endpoint or bridge are PCIe 
1.0. I don't expect this to cause problems, but if it does there's 
plenty of time to revert it.

-- 
Matthew Garrett | mjg59 at srcf.ucam.org