Some host bridges advertise non-prefetable memory windows that are
entirely located below 4GB but are marked as 64-bit address memory.
Since commit 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource
flags for 64-bit memory addresses"), the OF PCI range parser takes a
stricter view and treats 64-bit address ranges as advertised while
before such ranges were treated as 32-bit.
A PCI-to-PCI bridges cannot forward 64-bit non-prefetchable memory
ranges. As a result, the change in behaviour due to the commit causes
allocation failure for devices that are connected behind PCI host
bridges modelled as PCI-to-PCI bridge and require non-prefetchable bus
addresses.
In order to not break platforms, override the 64-bit flag for
non-prefetchable memory ranges that lie entirely below 4GB.
Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Link: https://lore.kernel.org/r/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@xxxxxxx
Signed-off-by: Punit Agrawal <punitagrawal@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
---
drivers/pci/of.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index da5b414d585a..b9d0bee5a088 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -565,10 +565,14 @@ static int pci_parse_request_of_pci_ranges(struct device *dev,
case IORESOURCE_MEM:
res_valid |= !(res->flags & IORESOURCE_PREFETCH);
- if (!(res->flags & IORESOURCE_PREFETCH))
+ if (!(res->flags & IORESOURCE_PREFETCH)) {
if (upper_32_bits(resource_size(res)))
dev_warn(dev, "Memory resource size exceeds max for 32 bits\n");
-
+ if ((res->flags & IORESOURCE_MEM_64) && !upper_32_bits(res->end)) {
+ dev_warn(dev, "Overriding 64-bit flag for non-prefetchable memory below 4GB\n");
+ res->flags &= ~IORESOURCE_MEM_64;
+ }
+ }
break;
}
}
--
2.30.2
