Re: [PATCH] ACPI / hotplug / PCI: Allocate resources directly under the non-hotplug bridge

Mika Westerberg
2019-11-07T14:03:04Z

On Thu, Nov 07, 2019 at 07:52:46AM -0600, Bjorn Helgaas wrote:
> > > What would happen if a device below one of the non-hotplug bridges,
> > > e.g., 3a:00.0, had an I/O BAR? Would this patch still work?
> >
> > I think it would still work because now we call pci_bus_size_bridges()
> > only for non-hotplug bridge which do not have I/O window open so
> > pbus_size_io() fails to find the "free" I/O resource on that bus and the
> > kernel then fails to assign that I/O resource for the device.
>
> Not sure I understand; are you saying that we wouldn't have the EC/GPE
> issue, but we'd be unable to use a device below 3a:00.0 that happened
> to have an I/O BAR?

Yes.

> That doesn't sound optimal because there is I/O space available that
> could be routed to 3a:00.0

If the none of the upstream bridges up to the PCIe root port does not
have I/O window open, I don't think we can do much about it. Unless I'm
missing something of course.