[PATCH] PPC: PCI: Fix pcibios_io_space_offset() so it works for 32-bit ptr/64-bit rsrcs

[Ben Collins]

The commit introducing pcibios_io_space_offset() was ignoring 32-bit to
64-bit sign extention, which is the case on ppc32 with 64-bit resource
addresses. This only seems to have shown up while running under QEMU for
e500mc target. It may or may be suboptimal that QEMU has an IO base
address > 32-bits for the e500-pci implementation, but 1) it's still a
regression and 2) it's more correct to handle things this way.

Signed-off-by: Ben Collins <bcollins at ubuntu.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
 arch/powerpc/kernel/pci-common.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 8e78e93..be9ced7 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -1477,9 +1477,15 @@ int pcibios_enable_device(struct pci_dev *dev, int mask)
 	return pci_enable_resources(dev, mask);
 }
 
+/* Before assuming too much here, take care to realize that we need sign
+ * extension from 32-bit pointers to 64-bit resource addresses to work.
+ */
 resource_size_t pcibios_io_space_offset(struct pci_controller *hose)
 {
-	return (unsigned long) hose->io_base_virt - _IO_BASE;
+	long vbase = (long)hose->io_base_virt;
+	long io_base = _IO_BASE;
+
+	return (resource_size_t)(vbase - io_base);
 }
 
 static void __devinit pcibios_setup_phb_resources(struct pci_controller *hose, struct list_head *resources)
-- 
1.7.9.5

--
Ben Collins
Servergy, Inc.
(757) 243-7557

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