This provides interfaces for drivers to discover the visible PCIe
requester ID for a device, for things like IOMMU setup, and iterate
over the device chain from requestee to requester, including DMA
quirks at each step.
Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
drivers/pci/search.c | 198 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/pci.h | 7 ++
2 files changed, 205 insertions(+)
diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index d0627fa..4759c02 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -18,6 +18,204 @@ DECLARE_RWSEM(pci_bus_sem);
EXPORT_SYMBOL_GPL(pci_bus_sem);
/*
+ * pci_has_pcie_requester_id - Does @dev have a PCIe requester ID
+ * @dev: device to test
+ */
+static bool pci_has_pcie_requester_id(struct pci_dev *dev)
+{
+ /*
+ * XXX There's no indicator of the bus type, conventional PCI vs
+ * PCI-X vs PCI-e, but we assume that a caller looking for a PCIe
+ * requester ID is a native PCIe based system (such as VT-d or
+ * AMD-Vi). It's common that PCIe root complex devices do not
+ * include a PCIe capability, but we can assume they are PCIe
+ * devices based on their topology.
+ */
+ if (pci_is_pcie(dev) || pci_is_root_bus(dev->bus))
+ return true;
+
+ /*
+ * PCI-X devices have a requester ID, but the bridge may still take
+ * ownership of transactions and create a requester ID. We therefore
+ * assume that the PCI-X requester ID is not the same one used on PCIe.
+ */
+
+#ifdef CONFIG_PCI_QUIRKS
+ /*
+ * Quirk for PCIe-to-PCI bridges which do not expose a PCIe capability.
+ * If the device is a bridge, look to the next device upstream of it.
+ * If that device is PCIe and not a PCIe-to-PCI bridge, then by
+ * deduction, the device must be PCIe and therefore has a requester ID.
+ */
+ if (dev->subordinate) {
+ struct pci_dev *parent = dev->bus->self;
+
+ if (pci_is_pcie(parent) &&
+ pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
+ return true;
+ }
+#endif
+
+ return false;
+}
+
+/*
+ * pci_has_visible_pcie_requester_id - Can @bridge see @dev's requester ID?
+ * @dev: requester device
+ * @bridge: upstream bridge (or NULL for root bus)
+ */
+static bool pci_has_visible_pcie_requester_id(struct pci_dev *dev,
+ struct pci_dev *bridge)
+{
+ /*
+ * The entire path must be tested, if any step does not have a
+ * requester ID, the chain is broken. This allows us to support
+ * topologies with PCIe requester ID gaps, ex: PCIe-PCI-PCIe
+ */
+ while (dev != bridge) {
+ if (!pci_has_pcie_requester_id(dev))
+ return false;
+
+ if (pci_is_root_bus(dev->bus))
+ return !bridge; /* false if we don't hit @bridge */
+
+ dev = dev->bus->self;
+ }
+
+ return true;
+}
+
+/*
+ * Legacy PCI bridges within a root complex (ex. Intel 82801) report
+ * a different requester ID than a standard PCIe-to-PCI bridge. Instead
+ * of using (subordinate << 8 | 0) the use (bus << 8 | devfn), like a
+ * standard PCIe endpoint. This function detects them.
+ *
+ * XXX Is this Intel vendor ID specific?
+ */
+static bool pci_bridge_uses_endpoint_requester(struct pci_dev *bridge)
+{
+ if (!pci_is_pcie(bridge) && pci_is_root_bus(bridge->bus))
+ return true;
+
+ return false;
+}
+
+#define PCI_REQUESTER_ID(dev) (((dev)->bus->number << 8) | (dev)->devfn)
+#define PCI_BRIDGE_REQUESTER_ID(dev) ((dev)->subordinate->number << 8)
+
+/*
+ * pci_get_visible_pcie_requester - Get requester and requester ID for
+ * @requestee below @bridge
+ * @requestee: requester device
+ * @bridge: upstream bridge (or NULL for root bus)
+ * @requester_id: location to store requester ID or NULL
+ */
+struct pci_dev *pci_get_visible_pcie_requester(struct pci_dev *requestee,
+ struct pci_dev *bridge,
+ u16 *requester_id)
+{
+ struct pci_dev *requester = requestee;
+
+ while (requester != bridge) {
+ requester = pci_get_dma_source(requester);
+ pci_dev_put(requester); /* XXX skip ref cnt */
+
+ if (pci_has_visible_pcie_requester_id(requester, bridge))
+ break;
+
+ if (pci_is_root_bus(requester->bus))
+ return NULL; /* @bridge not parent to @requestee */
+
+ requester = requester->bus->self;
+ }
+
+ if (requester_id) {
+ if (requester->bus != requestee->bus &&
+ !pci_bridge_uses_endpoint_requester(requester))
+ *requester_id = PCI_BRIDGE_REQUESTER_ID(requester);
+ else
+ *requester_id = PCI_REQUESTER_ID(requester);
+ }
+
+ return requester;
+}
+
+static int pci_do_requester_callback(struct pci_dev **dev,
+ int (*fn)(struct pci_dev *,
+ u16 id, void *),
+ void *data)
+{
+ struct pci_dev *dma_dev;
+ int ret;
+
+ ret = fn(*dev, PCI_REQUESTER_ID(*dev), data);
+ if (ret)
+ return ret;
+
+ dma_dev = pci_get_dma_source(*dev);
+ pci_dev_put(dma_dev); /* XXX skip ref cnt */
+ if (dma_dev == *dev)
+ return 0;
+
+ ret = fn(dma_dev, PCI_REQUESTER_ID(dma_dev), data);
+ if (ret)
+ return ret;
+
+ *dev = dma_dev;
+ return 0;
+}
+
+/*
+ * pcie_for_each_requester - Call callback @fn on each devices and DMA source
+ * from @requestee to the PCIe requester ID visible
+ * to @bridge.
+ * @requestee: Starting device
+ * @bridge: upstream bridge (or NULL for root bus)
+ * @fn: callback function
+ * @data: data to pass to callback
+ */
+int pcie_for_each_requester(struct pci_dev *requestee, struct pci_dev *bridge,
+ int (*fn)(struct pci_dev *, u16 id, void *),
+ void *data)
+{
+ struct pci_dev *requester;
+ struct pci_dev *dev = requestee;
+ int ret = 0;
+
+ requester = pci_get_visible_pcie_requester(requestee, bridge, NULL);
+ if (!requester)
+ return -EINVAL;
+
+ do {
+ ret = pci_do_requester_callback(&dev, fn, data);
+ if (ret)
+ return ret;
+
+ if (dev == requester)
+ return 0;
+
+ /*
+ * We always consider root bus devices to have a visible
+ * requester ID, therefore this should never be true.
+ */
+ BUG_ON(pci_is_root_bus(dev->bus));
+
+ dev = dev->bus->self;
+
+ } while (dev != requester);
+
+ /*
+ * If we've made it here, @requester is a bridge upstream from
+ * @requestee.
+ */
+ if (pci_bridge_uses_endpoint_requester(requester))
+ return pci_do_requester_callback(&requester, fn, data);
+
+ return fn(requester, PCI_BRIDGE_REQUESTER_ID(requester), data);
+}
+
+/*
* 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
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 3a24e4f..94e81d1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1873,6 +1873,13 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
}
#endif
+struct pci_dev *pci_get_visible_pcie_requester(struct pci_dev *requestee,
+ struct pci_dev *bridge,
+ u16 *requester_id);
+int pcie_for_each_requester(struct pci_dev *requestee, struct pci_dev *bridge,
+ int (*fn)(struct pci_dev *, u16 id, void *),
+ void *data);
+
/**
* pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a device
* @pdev: the PCI device
--
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