1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4859669f0ab5..557218222826 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1546,6 +1546,41 @@ void pci_enable_ari(struct pci_dev *dev)
 }
 
 /**
+ * pci_enable_acs - enable ACS if hardware support it
+ * @dev: the PCI device
+ */
+void pci_enable_acs(struct pci_dev *dev)
+{
+        int pos;
+        u16 cap;
+        u16 ctrl;
+
+        if (!dev->is_pcie)
+                return;
+
+        pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+        if (!pos)
+                return;
+
+        pci_read_config_word(dev, pos + PCI_ACS_CAP, &cap);
+        pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
+
+        /* Source Validation */
+        ctrl |= (cap & PCI_ACS_SV);
+
+        /* P2P Request Redirect */
+        ctrl |= (cap & PCI_ACS_RR);
+
+        /* P2P Completion Redirect */
+        ctrl |= (cap & PCI_ACS_CR);
+
+        /* Upstream Forwarding */
+        ctrl |= (cap & PCI_ACS_UF);
+
+        pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
+}
+
+/**
  * 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)