1 files changed, 69 insertions, 0 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 447e83472c01..1ccf7d49f522 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2360,6 +2360,75 @@ void pci_enable_acs(struct pci_dev *dev)
 }
 
 /**
+ * pci_acs_enabled - test ACS against required flags for a given device
+ * @pdev: device to test
+ * @acs_flags: required PCI ACS flags
+ *
+ * Return true if the device supports the provided flags.  Automatically
+ * filters out flags that are not implemented on multifunction devices.
+ */
+bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags)
+{
+        int pos, ret;
+        u16 ctrl;
+
+        ret = pci_dev_specific_acs_enabled(pdev, acs_flags);
+        if (ret >= 0)
+                return ret > 0;
+
+        if (!pci_is_pcie(pdev))
+                return false;
+
+        /* Filter out flags not applicable to multifunction */
+        if (pdev->multifunction)
+                acs_flags &= (PCI_ACS_RR | PCI_ACS_CR |
+                              PCI_ACS_EC | PCI_ACS_DT);
+
+        if (pdev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM ||
+            pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT ||
+            pdev->multifunction) {
+                pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
+                if (!pos)
+                        return false;
+
+                pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
+                if ((ctrl & acs_flags) != acs_flags)
+                        return false;
+        }
+
+        return true;
+}
+
+/**
+ * pci_acs_path_enable - test ACS flags from start to end in a hierarchy
+ * @start: starting downstream device
+ * @end: ending upstream device or NULL to search to the root bus
+ * @acs_flags: required flags
+ *
+ * Walk up a device tree from start to end testing PCI ACS support.  If
+ * any step along the way does not support the required flags, return false.
+ */
+bool pci_acs_path_enabled(struct pci_dev *start,
+                          struct pci_dev *end, u16 acs_flags)
+{
+        struct pci_dev *pdev, *parent = start;
+
+        do {
+                pdev = parent;
+
+                if (!pci_acs_enabled(pdev, acs_flags))
+                        return false;
+
+                if (pci_is_root_bus(pdev->bus))
+                        return (end == NULL);
+
+                parent = pdev->bus->self;
+        } while (pdev != end);
+
+        return true;
+}
+
+/**
  * pci_swizzle_interrupt_pin - swizzle INTx for device behind bridge
  * @dev: the PCI device
  * @pin: the INTx pin (1=INTA, 2=INTB, 3=INTD, 4=INTD)