[PATCH v3 8/8] PCI/quirks: Avoid certain address on Genoa systems

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

While testing the resource placement changes, tests hit a case where
igb fails to probe when BAR 0 is placed at 0x9c000000:

   90000000-9cffffff : PCI Bus 0000:a0
  -  90000000-902fffff : PCI Bus 0000:a1
  -    90000000-900fffff : 0000:a1:00.0
  -      90000000-900fffff : igb
  -    90100000-901fffff : 0000:a1:00.0
  -    90200000-90203fff : 0000:a1:00.0
  -      90200000-90203fff : igb
  +  9be00000-9c0fffff : PCI Bus 0000:a1
  +    9be00000-9befffff : 0000:a1:00.0
  +    9bf00000-9bf03fff : 0000:a1:00.0
  +    9c000000-9c0fffff : 0000:a1:00.0
     9c100000-9c17ffff : amd_iommu
     9c180000-9c1803ff : IOAPIC 8

  -       Region 0: Memory at 90000000 (32-bit, non-prefetchable) [size=1M]
  -       Region 3: Memory at 90200000 (32-bit, non-prefetchable) [size=16K]
  -       Expansion ROM at 90100000 [disabled] [size=1M]
  +       Region 0: Memory at 9c000000 (32-bit, non-prefetchable) [size=1M]
  +       Region 3: Memory at 9bf00000 (32-bit, non-prefetchable) [size=16K]
  +       Expansion ROM at 9be00000 [disabled] [size=1M]

igb 0000:a1:00.0 0000:a1:00.0 (uninitialized): PCIe link lost
------------[ cut here ]------------
igb: Failed to read reg 0x18!
WARNING: drivers/net/ethernet/intel/igb/igb_main.c:724 at igb_rd32.cold+0x3c/0x4f [igb], CPU#32: kworker/32:1/706
...
 igb_get_invariants_82575+0xff/0xf00 [igb]
 igb_probe+0x3c8/0x1190 [igb]
 local_pci_probe+0x3b/0x80

It turns out there is a 64kB iomem black hole at 9c000000 that returns
~0 and this is where igb's BAR 0 resides. If another BAR of the same
card is placed into that address, it is similarly black holed.

Mark the problematic 64kB range reserved using a quirk bound to the
bridge found in the problematic system.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=222074
Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
Cc: Borislav Petkov <bp@alien8.de>

As an alternative to this, I've also tested reverting the commit
07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map") and
that also resolves the issue by retaining "9c000000-9cffffff : Reserved"
entry in the resource tree.

---
 arch/x86/pci/fixup.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index b301c6c8df75..cc463bf492b6 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -822,6 +822,42 @@ DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, 0x1571, pci_amd_enable_64bit_bar);
 DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, 0x15b1, pci_amd_enable_64bit_bar);
 DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, 0x1601, pci_amd_enable_64bit_bar);
 
+/*
+ * TODO: Remove when/if root cause is found.
+ *
+ * Genoa appears to have a 64kB iomem black hole starting at 0x9c000000
+ * address for which all reads return ~0 blocking an overlapping BAR from
+ * working.
+ *
+ * Work around the problem by reserving the space prior to making any iomem
+ * allocations that could overlap with the black hole.
+ */
+static struct resource genoa_black_hole = DEFINE_RES_MEM_NAMED(0x9c000000,
+							       SZ_64K,
+							       "reserved");
+
+static void genoa_iomem_black_hole(struct pci_dev *dev)
+{
+	struct resource *r;
+
+	pci_bus_for_each_resource(dev->bus, r) {
+		if (!r || !r->flags || !resource_assigned(r))
+			continue;
+
+		if (!__resource_contains_unbound(r, &genoa_black_hole))
+			continue;
+
+		if (resource_assigned(&genoa_black_hole))
+			pci_dbg(dev, "iomem black hole workaround already applied\n");
+		else if (!insert_resource(r, &genoa_black_hole))
+			pci_info(dev, "iomem black hole workaround enabled\n");
+		else
+			pci_dbg(dev, "iomem black hole workaround add failed\n");
+		return;
+	}
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, 0x14ab, genoa_iomem_black_hole);
+
 #define RS690_LOWER_TOP_OF_DRAM2	0x30
 #define RS690_LOWER_TOP_OF_DRAM2_VALID	0x1
 #define RS690_UPPER_TOP_OF_DRAM2	0x31
-- 
2.47.3