PCI: Add PCI_BRIDGE_NO_ALIASES quirk for ASPEED AST1150

ASPEED BMC controllers have VGA and USB functions behind a PCIe-to-PCI
bridge that causes them to share the same stream ID:

  [e0]---00.0-[e1-e2]----00.0-[e2]--+-00.0  ASPEED Graphics Family
                                    \-02.0  ASPEED USB Controller

Both devices get stream ID 0x5e200 due to bridge aliasing, causing the
USB controller to be rejected with 'Aliasing StreamID unsupported'.

Per ASPEED, the AST1150 doesn't use a real PCI bus and always forwards
the original requester ID from downstream devices rather than replacing
it with any alias.

Add a new PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES flag and apply it to the
AST1150.

Suggested-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Robin Murphy <[email protected]>
Signed-off-by: Nirmoy Das <[email protected]>
(backported from https://lore.kernel.org/linux-iommu/[email protected]/)
[nirmoy: set PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES to  (1 << 15) instead of (1 << 14)]
Signed-off-by: Nirmoy Das <[email protected]>

Author: nirmoy

drivers/pci/quirks.c

@@ -4476,6 +4476,16 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9000,
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9084,
 				quirk_bridge_cavm_thrx2_pcie_root);
 
+/*
+ * AST1150 doesn't use a real PCI bus and always forwards the requester ID
+ * from downstream devices.
+ */
+static void quirk_aspeed_pci_bridge_no_aliases(struct pci_dev *pdev)
+{
+	pdev->dev_flags |= PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ASPEED, 0x1150, quirk_aspeed_pci_bridge_no_aliases);
+
 /*
  * Intersil/Techwell TW686[4589]-based video capture cards have an empty (zero)
  * class code.  Fix it.

drivers/pci/search.c

@@ -86,6 +86,8 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
 			case PCI_EXP_TYPE_DOWNSTREAM:
 				continue;
 			case PCI_EXP_TYPE_PCI_BRIDGE:
+				if (tmp->dev_flags & PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES)
+					continue;
 				ret = fn(tmp,
 					 PCI_DEVID(tmp->subordinate->number,
 						   PCI_DEVFN(0, 0)), data);

include/linux/pci.h

@@ -249,6 +249,11 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_MSIX_TOUCH_ENTRY_DATA_FIRST = (__force pci_dev_flags_t) (1 << 13),
 	/* Do not use Configuration Request Retry Status polling in pci_dev_wait() */
 	PCI_DEV_FLAGS_NO_RRS_SV = (__force pci_dev_flags_t) (1 << 14),
+	/*
+	 * PCIe to PCI bridge does not create RID aliases because the bridge is
+	 * integrated with the downstream devices and doesn't use real PCI.
+	 */
+	PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIASES = (__force pci_dev_flags_t) (1 << 15),
 };
 
 enum pci_irq_reroute_variant {