Hi !
While working on consolidating resource assignment, I stumbled upon
something alpha does (and maybe others I haven't spotted yet):
On most platforms (not all), it uses the usual pair:
pci_bus_size_bridges(bus);
pci_bus_assign_resources(bus);
to reassign everything.
However, before doing so, it first calls pcibios_claim_one_bus() which,
on those platforms (ie those who don't set PCI_PROBE_ONLY), will
effectively claim only resources that have IORESOURCE_PCI_FIXED.
Now, let's leave alone for now the fact that this is will really only
work if those resources aren't behind a bridge as, to the best of my
undertanding of the code at this point, we aren't going to take them
into account when sizing & locating bridges. But that's not my point
right now :-)
>From what I can tell, these days, pci_bus_assign_resources() will
already claim those fixed resources via pdev_assign_fixed_resources().
However, it does so *after* it has assigned and claimed resoures for
all the sibling devices on that bus.
That looks wrong to me. Shouldn't we claim the fixed resources first ?
IE something like:
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1345,11 +1345,12 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
struct pci_bus *b;
struct pci_dev *dev;
+ list_for_each_entry(dev, &bus->devices, bus_list)
+ pdev_assign_fixed_resources(dev);
+
pbus_assign_resources_sorted(bus, realloc_head, fail_head);
list_for_each_entry(dev, &bus->devices, bus_list) {
- pdev_assign_fixed_resources(dev);
-
b = dev->subordinate;
if (!b)
continue;
?
Now, I suspect most of the time it happens to work due to the fact that
the fixed resources are generally IO resources in the legacy low ranges
( < 0x1000) and PCIBIOS_MIN_IO is *generally* set to 0x1000 but it still
sounds fishy to me.
I don't think I have HW at hand with that type of fixed stuff to test
with at the moment, so this is very much academic right now but I worry
that when I convert archs such as alpha who does that claiming before
the rest of the assignment, switching doing things the other way around
will break.
Any thoughts ?
Cheers,
Ben.
