[PATCH v2 1/2] PCI: Add PCI device flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT

[Jayachandran C <jchandra@broadcom.com>]

Add a new flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT to limit the DMA alias
search to go no further than the bridge where the IOMMU is attached.

This has been added to support Broadcom's Vulcan which has the SMMUv3
and GIC ITS associated with an intermediate bridge in the PCI topology.
Traversing to buses above would hit internal glue bridges which will
change the RID.

Update the function pci_for_each_dma_alias() to stop when it see a
bridge with this flag set.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
---

Here is v2 of the patch, the previous discussion is at 
http://lists.linuxfoundation.org/pipermail/iommu/2016-February/015668.html

v1->v2 changes:
 - dropped the BAR quirk (not needed)
 - moved from using the 'skip' flag for some bridges to using
   similar approach to stop the traversal at the bridge with
   PCI_DEV_FLAGS_DMA_ALIAS_ROOT

Comments and suggestions are welcome

JC.

 drivers/pci/search.c | 4 ++++
 include/linux/pci.h  | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index a20ce7d..3ea9c27 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -56,6 +56,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
 
 		tmp = bus->self;
 
+		/* stop at bridge where translation unit is associated */
+		if (tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_ROOT)
+			return ret;
+
 		/*
 		 * PCIe-to-PCI/X bridges alias transactions from downstream
 		 * devices using the subordinate bus number (PCI Express to
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 932ec74..b6f832b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -176,6 +176,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7),
 	/* Get VPD from function 0 VPD */
 	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8),
+	/* a non-root bridge where translation occurs, stop alias search here */
+	PCI_DEV_FLAGS_DMA_ALIAS_ROOT = (__force pci_dev_flags_t) (1 << 9),
 };
 
 enum pci_irq_reroute_variant {
-- 
1.9.1