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authorAlex Williamson <alex.williamson@redhat.com>2014-05-22 17:07:30 -0600
committerBjorn Helgaas <bhelgaas@google.com>2014-05-28 11:46:24 -0600
commitc25dc82899e67a32fdcfb20dd72a37fc236fde2e (patch)
tree5db0bd880c1b2fbfb3435e68b991216e2a770cf2 /drivers/pci
parentc9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff)
downloadop-kernel-dev-c25dc82899e67a32fdcfb20dd72a37fc236fde2e.zip
op-kernel-dev-c25dc82899e67a32fdcfb20dd72a37fc236fde2e.tar.gz
PCI: Add DMA alias iterator
In a mixed PCI/PCI-X/PCIe topology, bridges can take ownership of transactions, replacing the original requester ID with their own. Sometimes we just want to know the resulting device or resulting alias; other times we want each step in the chain. This iterator allows either usage. When an endpoint is connected via an unbroken chain of PCIe switches and root ports, it has no alias and its requester ID is visible to the root bus. When PCI/X get in the way, we pick up aliases for bridges. The reason why we potentially care about each step in the path is because of PCI-X. PCI-X has the concept of a requester ID, but bridges may or may not take ownership of various types of transactions. We therefore leave it to the consumer of this function to prune out what they don't care about rather than attempt to flatten the alias ourselves. Tested-by: George Spelvin <linux@horizon.com> Tested-by: Pat Erley <pat-lkml@erley.org> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci')
-rw-r--r--drivers/pci/search.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 4a1b972..5601cdb 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -18,6 +18,76 @@ DECLARE_RWSEM(pci_bus_sem);
EXPORT_SYMBOL_GPL(pci_bus_sem);
/*
+ * pci_for_each_dma_alias - Iterate over DMA aliases for a device
+ * @pdev: starting downstream device
+ * @fn: function to call for each alias
+ * @data: opaque data to pass to @fn
+ *
+ * Starting @pdev, walk up the bus calling @fn for each possible alias
+ * of @pdev at the root bus.
+ */
+int pci_for_each_dma_alias(struct pci_dev *pdev,
+ int (*fn)(struct pci_dev *pdev,
+ u16 alias, void *data), void *data)
+{
+ struct pci_bus *bus;
+ int ret;
+
+ ret = fn(pdev, PCI_DEVID(pdev->bus->number, pdev->devfn), data);
+ if (ret)
+ return ret;
+
+ for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) {
+ struct pci_dev *tmp;
+
+ /* Skip virtual buses */
+ if (!bus->self)
+ continue;
+
+ tmp = bus->self;
+
+ /*
+ * PCIe-to-PCI/X bridges alias transactions from downstream
+ * devices using the subordinate bus number (PCI Express to
+ * PCI/PCI-X Bridge Spec, rev 1.0, sec 2.3). For all cases
+ * where the upstream bus is PCI/X we alias to the bridge
+ * (there are various conditions in the previous reference
+ * where the bridge may take ownership of transactions, even
+ * when the secondary interface is PCI-X).
+ */
+ if (pci_is_pcie(tmp)) {
+ switch (pci_pcie_type(tmp)) {
+ case PCI_EXP_TYPE_ROOT_PORT:
+ case PCI_EXP_TYPE_UPSTREAM:
+ case PCI_EXP_TYPE_DOWNSTREAM:
+ continue;
+ case PCI_EXP_TYPE_PCI_BRIDGE:
+ ret = fn(tmp,
+ PCI_DEVID(tmp->subordinate->number,
+ PCI_DEVFN(0, 0)), data);
+ if (ret)
+ return ret;
+ continue;
+ case PCI_EXP_TYPE_PCIE_BRIDGE:
+ ret = fn(tmp,
+ PCI_DEVID(tmp->bus->number,
+ tmp->devfn), data);
+ if (ret)
+ return ret;
+ continue;
+ }
+ } else {
+ ret = fn(tmp, PCI_DEVID(tmp->bus->number, tmp->devfn),
+ data);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return ret;
+}
+
+/*
* find the upstream PCIe-to-PCI bridge of a PCI device
* if the device is PCIE, return NULL
* if the device isn't connected to a PCIe bridge (that is its parent is a
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