On Saturday, June 11, 2016 12:43 AM, Bjorn Helgaas wrote:
> On Wed, Jun 08, 2016 at 05:32:44PM +0800, Rui Wang wrote:
> > @@ -1779,8 +1780,12 @@ void __init
> > pci_assign_unassigned_resources(void)
> > {
> > struct pci_bus *root_bus;
> >
> > - list_for_each_entry(root_bus, &pci_root_buses, node)
> > + list_for_each_entry(root_bus, &pci_root_buses, node) {
> > pci_assign_unassigned_root_bus_resources(root_bus);
> > +#ifdef CONFIG_X86
> > + acpi_ioapic_add(ACPI_HANDLE(root_bus->bridge));
> > +#endif
>
> This seems like a strange place to call acpi_ioapic_add(). Your object is to
> call
> acpi_ioapic_add() during root bus enumeration.
>
> I assume we *can't* call acpi_ioapic_add() from acpi_pci_root_add() at boot
> time, for some reason you'll explain. But is there a reason we have to call
> it
> from pci_assign_unassigned_resources() (where it requires an ifdef) instead
> of from pcibios_assign_resources(), which is already x86-specific?
>
> In acpi_pci_root_add(), we have this:
>
> acpi_pci_root_add(...)
> {
> ...
> if (hotadd)
> acpi_ioapic_add(root);
>
> So the obvious question is why don't we just remove the "if (hotadd)"
> and call acpi_ioapic_add() always.
>
> I'm sure the reason is some ordering problem, but we need a comment in
> acpi_pci_root_add() about why the obvious solution doesn't work.
>
Hi Bjorn,
Yes it's an ording issue. acpi_ioapic_add() and also ioapic_insert_resources()
have to be later than pci initialization in order to deal with IOAPICs mapped
on a PCI BAR. There's a comment about this inside pcibios_resource_survey()
above ioapic_insert_resources(). We can also add a comment inside
acpi_pci_root_add(), though.
And yes calling acpi_ioapic_add() in pcibios_assign_resources() doesn't require
ifdef CONFIG_X86. But it'll require a loop to iterate through the root buses,
and call acpi_ioapic_add() within the loop. pci_assign_unassigned_resources()
already has that loop. Do you still prefer adding it to
pcibios_assign_resources() ?
Regards,
Rui
