PCI: Align bridge I/O windows as required by downstream devices & bridges

An upstream bridge's I/O window must be at least as aligned as any
downstream device or bridge requires.  In particular, if the upstream
bridge supports 1K alignment but a downstream bridge requires 4K alignment,
the upstream window must also be 4K aligned.

Therefore, do not reduce the required alignment ("min_align") based on
the upstream bridge's capabilities.

Reported-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index d4f1ad956fad..8333c92c2027 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -749,12 +749,12 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
         struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
         resource_size_t size = 0, size0 = 0, size1 = 0;
         resource_size_t children_add_size = 0;
-        resource_size_t min_align, io_align, align;
+        resource_size_t min_align, align;
 
         if (!b_res)
                 return;
 
-        io_align = min_align = window_alignment(bus, IORESOURCE_IO);
+        min_align = window_alignment(bus, IORESOURCE_IO);
         list_for_each_entry(dev, &bus->devices, bus_list) {
                 int i;
 
@@ -781,9 +781,6 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
                 }
         }
 
-        if (min_align > io_align)
-                min_align = io_align;
-
         size0 = calculate_iosize(size, min_size, size1,
                         resource_size(b_res), min_align);
         if (children_add_size > add_size)