PCI: Enable ARI if dev and upstream bridge support it; disable otherwise

commit b0cc6020e1cc62f1253215f189611b34be4a83c7 upstream.

Currently, we enable ARI in a device's upstream bridge if the bridge and
the device support it.  But we never disable ARI, even if the device is
removed and replaced with a device that doesn't support ARI.

This means that if we hot-remove an ARI device and replace it with a
non-ARI multi-function device, we find only function 0 of the new device
because the upstream bridge still has ARI enabled, and next_ari_fn()
only returns function 0 for the new non-ARI device.

This patch disables ARI in the upstream bridge if the device doesn't
support ARI.  See the PCIe spec, r3.0, sec 6.13.

[bhelgaas: changelog, function comment]
[yijing: replace PCIe Cap accessor with legacy PCI accessor]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 363a5c6..9f1fec1 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1915,10 +1915,6 @@ void pci_enable_ari(struct pci_dev *dev)
        if (!pci_is_pcie(dev) || dev->devfn)
                return;
 
-       pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
-       if (!pos)
-               return;
-
        bridge = dev->bus->self;
        if (!bridge || !pci_is_pcie(bridge))
                return;
@@ -1937,10 +1933,14 @@ void pci_enable_ari(struct pci_dev *dev)
                return;
 
        pci_read_config_word(bridge, pos + PCI_EXP_DEVCTL2, &ctrl);
-       ctrl |= PCI_EXP_DEVCTL2_ARI;
+       if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI)) {
+               ctrl |= PCI_EXP_DEVCTL2_ARI;
+               bridge->ari_enabled = 1;
+       } else {
+               ctrl &= ~PCI_EXP_DEVCTL2_ARI;
+               bridge->ari_enabled = 0;
+       }
        pci_write_config_word(bridge, pos + PCI_EXP_DEVCTL2, ctrl);
-
-       bridge->ari_enabled = 1;
 }
 
 /**