PCI: of: Clear 64-bit flag for non-prefetchable memory below 4GB

Alexandru and Qu reported this resource allocation failure on ROCKPro64 v2
and ROCK Pi 4B, both based on the RK3399:

  pci_bus 0000:00: root bus resource [mem 0xfa000000-0xfbdfffff 64bit]
  pci 0000:00:00.0: PCI bridge to [bus 01]
  pci 0000:00:00.0: BAR 14: no space for [mem size 0x00100000]
  pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x00003fff 64bit]

"BAR 14" is the PCI bridge's 32-bit non-prefetchable window, and our PCI
allocation code isn't smart enough to allocate it in a host bridge window
marked as 64-bit, even though this should work fine.

A DT host bridge description includes the windows from the CPU address
space to the PCI bus space.  On a few architectures (microblaze, powerpc,
sparc), the DT may also describe PCI devices themselves, including their
BARs.

Before 9d57e61 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for
64-bit memory addresses"), of_bus_pci_get_flags() ignored the fact that
some DT addresses described 64-bit windows and BARs.  That was a problem
because the virtio virtual NIC has a 32-bit BAR and a 64-bit BAR, and the
driver couldn't distinguish them.

9d57e61 set IORESOURCE_MEM_64 for those 64-bit DT ranges, which fixed
the virtio driver.  But it also set IORESOURCE_MEM_64 for host bridge
windows, which exposed the fact that the PCI allocator isn't smart enough
to put 32-bit resources in those 64-bit windows.

Clear IORESOURCE_MEM_64 from host bridge windows since we don't need that
information.

Suggested-by: Bjorn Helgaas <[email protected]>
Fixes: 9d57e61 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses")
Link: https://lore.kernel.org/r/[email protected]
Reported-at: https://lore.kernel.org/lkml/[email protected]/
Reported-at: https://lore.kernel.org/lkml/YMyTUv7Jsd89PGci@m4/T/#u
Reported-by: Alexandru Elisei <[email protected]>
Reported-by: Qu Wenruo <[email protected]>
Tested-by: Alexandru Elisei <[email protected]>
Tested-by: Domenico Andreoli <[email protected]>
Signed-off-by: Punit Agrawal <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>

drivers/pci/of.c

@@ -346,6 +346,8 @@ static int devm_of_pci_get_host_bridge_resources(struct device *dev,
 				dev_warn(dev, "More than one I/O resource converted for %pOF. CPU base address for old range lost!\n",
 					 dev_node);
 			*io_base = range.cpu_addr;
+		} else if (resource_type(res) == IORESOURCE_MEM) {
+			res->flags &= ~IORESOURCE_MEM_64;
 		}
 
 		pci_add_resource_offset(resources, res,	res->start - range.pci_addr);