PCI: fix ARI code to be compatible with mixed ARI/non-ARI systems

The original ARI support code has a compatibility problem with non-ARI
devices.  If a device doesn't support ARI, turning on ARI forwarding on
its upper level bridge will cause undefined behavior.

This fix turns on ARI forwarding only when the subordinate devices
support it.

Tested-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 533aeb5fcbe4512cb97c6244e7d41ba35cc9c4ed..21f2ac639cab2f31937971113fe9872275cfd9a0 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1309,27 +1309,32 @@ void pci_enable_ari(struct pci_dev *dev)
        int pos;
        u32 cap;
        u16 ctrl;
+       struct pci_dev *bridge;
 
-       if (!dev->is_pcie)
+       if (!dev->is_pcie || dev->devfn)
                return;
 
-       if (dev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
-           dev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
+       pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
+       if (!pos)
                return;
 
-       pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
+       bridge = dev->bus->self;
+       if (!bridge || !bridge->is_pcie)
+               return;
+
+       pos = pci_find_capability(bridge, PCI_CAP_ID_EXP);
        if (!pos)
                return;
 
-       pci_read_config_dword(dev, pos + PCI_EXP_DEVCAP2, &cap);
+       pci_read_config_dword(bridge, pos + PCI_EXP_DEVCAP2, &cap);
        if (!(cap & PCI_EXP_DEVCAP2_ARI))
                return;
 
-       pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
+       pci_read_config_word(bridge, pos + PCI_EXP_DEVCTL2, &ctrl);
        ctrl |= PCI_EXP_DEVCTL2_ARI;
-       pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
+       pci_write_config_word(bridge, pos + PCI_EXP_DEVCTL2, ctrl);
 
-       dev->ari_enabled = 1;
+       bridge->ari_enabled = 1;
 }
 
 int