On Mon, Jun 14, 2021 at 5:05 PM Punit Agrawal [off-list ref] wrote:

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 9d57e61bf723 ("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.

9d57e61bf723 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.

Fixes: 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses")
Reported-at: https://lore.kernel.org/lkml/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@arm.com/ (local)
Reported-by: Alexandru Elisei <redacted>
Reported-by: Qu Wenruo <redacted>
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Punit Agrawal <redacted>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Rob Herring <robh+dt@kernel.org>

I think we've beat this one to death.

Reviewed-by: Rob Herring <robh@kernel.org>

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