[RFC PATCH 3/3] PCI: do not reset bridge's IORESOURCE_MEM_64 flag for ROM BAR

[Guo Chao <yan@linux.vnet.ibm.com>]

If 32-bit prefetchable BARs detected, the prefetchable resource's
IORESOURCE_MEM_64 flag of its upstream bridge will be reset. This in
turn causes all upstream bridges up to the root bridge have their
IORESOURCE_MEM_64 reset. If prefetchable windows in a system located
above 4G, then they are never used for the sake of 32-bit prefetchable BAR.

Desert 64-bit prefetchable windows for ROM BAR seems unreasonable.
Just don't reset bridge's IORESOURCE_MEM_64 flag in case of ROM BARs.
They will fail to get address from 4G-above prefetchable window and
fall back to non-prefetchable window within 4G.

Signed-off-by: Guo Chao <yan@linux.vnet.ibm.com>
---
 drivers/pci/setup-bus.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 4ce83b2..e9006b9 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -974,7 +974,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 				aligns[order] += align;
 			if (order > max_order)
 				max_order = order;
-			mem64_mask &= r->flags & IORESOURCE_MEM_64;
+			if (i != PCI_ROM_RESOURCE)
+				mem64_mask &= r->flags & IORESOURCE_MEM_64;
 
 			if (realloc_head)
 				children_add_size += get_res_add_size(realloc_head, r);
-- 
1.8.3.2