Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

Arjan van de Ven
2008-01-14T16:02:42Z

On Mon, 14 Jan 2008 10:23:14 -0500
Tony Camuso <tcamuso@redhat.com> wrote:

> Arjan van de Ven wrote:
> > On Mon, 14 Jan 2008 08:01:01 -0500
> > Tony Camuso <tcamuso@redhat.com> wrote:
> >>
> >> If we're going to differentiate MMCONFIG from
> >> some other access mechanism, it only needs to be done at the
> >> Northbridge level. Devices are electrically ignorant of the
> >> protocol used between CPU and Northbridge to get the Northbridge
> >> to assert config cycles on the bus.
> >
> > Again this is about having systems that don't need extended config
> > space not use it. At all. The only way to do that is have the
> > drivers say they need it, and not use it otherwise. It has NOTHING
> > to do with how things are wired up. It's pure a kernel level policy
> > decision about whether to use extended config space AT ALL.
> >
>
> The problem with compelling device drivers to determine the PCI
> config mechanism is that it must be forced upon arches that
> have no PCI configuration quirks or don't even use the same
> PCI config mechanisms as x86.

it's not pci_enable_mmconf(), it's pci_enable_extended_config_space... it's independent of the mechanism!

>
> I don't think that's a good policy.
>
> Better to confine arch-specific quirks to the arch-specific code
> whenever possible.
>

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