Re: [PATCH V6 3/5] PCI: thunder-pem: Allow to probe PEM-specific register range for ACPI case

From: Bjorn Helgaas
Date: Wed Sep 21 2016 - 15:19:30 EST

On Wed, Sep 21, 2016 at 11:58:22AM -0700, Duc Dang wrote:
> On Wed, Sep 21, 2016 at 11:04 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > On Wed, Sep 21, 2016 at 03:05:49PM +0100, Lorenzo Pieralisi wrote:

> > The existing x86 practice is to use PNP0C02 devices for this purpose,
> > and I think we should just follow that practice.
> >
> > ...
> >
> > My point is that the hard-coding should not be buried in a driver
> > where it's invisible to the rest of the kernel. If we hard-code it in
> > a quirk that adds _CRS entries, then the kernel will work just like it
> > would if the firmware had been correct in the first place. The
> > resource will appear in /sys/devices/pnp*/*/resources and /proc/iomem,
> > and if we ever used _SRS to assign or move ACPI devices, we would know
> > to avoid the bridge resource.
> Are you suggesting to add code similar to functions in
> linux/drivers/pnp/quirks.c to declare/attach the additional resource
> that the host need to have when the resource is not in MCFG table?

Yes, but what I'm suggesting is actually a little stronger. This has
nothing to do with whether a resource is in the MCFG table or not.

I'm suggesting ACPI firmware should always describe the resource. If the
firmware is defective and doesn't describe it, we should add a quirk in
pnp/quirks.c to add a resource for it.