[SRU][N:gke][PATCH 070/106] PCI: Use downstream bridges for distributing resources

[Tim Whisonant]

From: Kai-Heng Feng <kaihengf at nvidia.com>

BugLink: https://bugs.launchpad.net/bugs/2117098

7180c1d08639 ("PCI: Distribute available resources for root buses, too")
breaks BAR assignment on some devices:

  pci 0006:03:00.0: BAR 0 [mem 0x6300c0000000-0x6300c1ffffff 64bit pref]: assigned
  pci 0006:03:00.1: BAR 0 [mem 0x6300c2000000-0x6300c3ffffff 64bit pref]: assigned
  pci 0006:03:00.2: BAR 0 [mem size 0x00800000 64bit pref]: can't assign; no space
  pci 0006:03:00.0: VF BAR 0 [mem size 0x02000000 64bit pref]: can't assign; no space
  pci 0006:03:00.1: VF BAR 0 [mem size 0x02000000 64bit pref]: can't assign; no space

The apertures of domain 0006 before 7180c1d08639:

  6300c0000000-63ffffffffff : PCI Bus 0006:00
    6300c0000000-6300c9ffffff : PCI Bus 0006:01
      6300c0000000-6300c9ffffff : PCI Bus 0006:02        # 160MB
        6300c0000000-6300c8ffffff : PCI Bus 0006:03      #   144MB
          6300c0000000-6300c1ffffff : 0006:03:00.0       #     32MB
          6300c2000000-6300c3ffffff : 0006:03:00.1       #     32MB
          6300c4000000-6300c47fffff : 0006:03:00.2       #      8MB
          6300c4800000-6300c67fffff : 0006:03:00.0       #     32MB
          6300c6800000-6300c87fffff : 0006:03:00.1       #     32MB
        6300c9000000-6300c9bfffff : PCI Bus 0006:04      #    12MB
          6300c9000000-6300c9bfffff : PCI Bus 0006:05    #    12MB
            6300c9000000-6300c91fffff : PCI Bus 0006:06  #      2MB
            6300c9200000-6300c93fffff : PCI Bus 0006:07  #      2MB
            6300c9400000-6300c95fffff : PCI Bus 0006:08  #      2MB
            6300c9600000-6300c97fffff : PCI Bus 0006:09  #      2MB

After 7180c1d08639:

  6300c0000000-63ffffffffff : PCI Bus 0006:00
    6300c0000000-6300c9ffffff : PCI Bus 0006:01
      6300c0000000-6300c9ffffff : PCI Bus 0006:02        # 160MB
        6300c0000000-6300c43fffff : PCI Bus 0006:03      #    68MB
          6300c0000000-6300c1ffffff : 0006:03:00.0       #      32MB
          6300c2000000-6300c3ffffff : 0006:03:00.1       #      32MB
              --- no space ---      : 0006:03:00.2       #       8MB
              --- no space ---      : 0006:03:00.0       #      32MB
              --- no space ---      : 0006:03:00.1       #      32MB
        6300c4400000-6300c4dfffff : PCI Bus 0006:04      #    10MB
          6300c4400000-6300c4dfffff : PCI Bus 0006:05    #      10MB
            6300c4400000-6300c45fffff : PCI Bus 0006:06  #        2MB
            6300c4600000-6300c47fffff : PCI Bus 0006:07  #        2MB
            6300c4800000-6300c49fffff : PCI Bus 0006:08  #        2MB
            6300c4a00000-6300c4bfffff : PCI Bus 0006:09  #        2MB

We can see that the window to 0006:03 gets shrunken too much and 0006:04
eats away the window for 0006:03:00.2.

The offending commit distributes the upstream bridge's resources multiple
times to every downstream bridge, hence makes the aperture smaller than
desired because calculation of io_per_b, mmio_per_b and mmio_pref_per_b
becomes incorrect.

Instead, distribute downstream bridges' own resources to resolve the issue.

Link: https://lore.kernel.org/r/20241204022457.51322-1-kaihengf@nvidia.com
Fixes: 7180c1d08639 ("PCI: Distribute available resources for root buses, too")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219540
Signed-off-by: Kai-Heng Feng <kaihengf at nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
Tested-by: Chia-Lin Kao (AceLan) <acelan.kao at canonical.com>
Reviewed-by: Mika Westerberg <mika.westerberg at linux.intel.com>
Cc: Carol Soto <csoto at nvidia.com>
Cc: Jonathan Cameron <Jonathan.Cameron at huawei.com>
Cc: Chris Chiu <chris.chiu at canonical.com>
(cherry picked from commit 1a596ad00ffe9b37fc60a93cbdd4daead3bf95f3)
Signed-off-by: Tim Whisonant <tim.whisonant at canonical.com>
---
 drivers/pci/setup-bus.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 141d6b31959be..41ed71c7ebbbf 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -2028,8 +2028,7 @@ pci_root_bus_distribute_available_resources(struct pci_bus *bus,
 		 * in case of root bus.
 		 */
 		if (bridge && pci_bridge_resources_not_assigned(dev))
-			pci_bridge_distribute_available_resources(bridge,
-								  add_list);
+			pci_bridge_distribute_available_resources(dev, add_list);
 		else
 			pci_root_bus_distribute_available_resources(b, add_list);
 	}
-- 
2.43.0