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authorYijing Wang <wangyijing@huawei.com>2015-05-21 10:05:03 +0300
committerBjorn Helgaas <bhelgaas@google.com>2015-05-26 20:56:47 +0300
commitc8fc9339409df88693742d323819ab8415cd2e9d (patch)
tree56e8d688204f8f8ffc36eb1962b8c156bced6440 /drivers
parentd0751b98dfa391f862e02dc36a233a54615e3f1d (diff)
downloadlinux-c8fc9339409df88693742d323819ab8415cd2e9d.tar.xz
PCI/ASPM: Use dev->has_secondary_link to find downstream links
We allocate pcie_link_state for the component at the upstream end of a Link. Previously we did this by allocating pcie_link_state for Root Ports and Downstream Ports. This works fine for the typical topology: 00:1c.0 Root Port [bridge to bus 02] 02:00.0 Upstream Port [bridge to bus 03] 03:00.0 Downstream Port [bridge to bus 04] 04:00.0 Endpoint or Switch Port However, it is possible to have a Root Port connected to a Downstream Port instead of an Upstream Port, as in Robert White's ATCA system: 00:1c.0 Root Port [bridge to bus 02] 02:00.0 Downstream Port [bridge to bus 03] 03:01.0 Downstream Port [bridge to bus 04] 04:00.0 Endpoint or Switch Port In this topology, we wrongly allocated pcie_link_state for the 02:00.0 Downstream Port, which is actually the *downstream* end of a link. This led to the following NULL pointer dereference when we tried to connect this link into the tree of links starting at the 00:1c.0 Root Port: BUG: unable to handle kernel NULL pointer dereference at 0000000000000088 IP: [<ffffffff81550324>] pcie_aspm_init_link_state+0x744/0x850 Hardware name: Kontron B3001/B3001, BIOS 4.6.3 08/07/2012 Call Trace: [<ffffffff8153b865>] pci_scan_slot+0xd5/0x120 [<ffffffff8153ca1d>] pci_scan_child_bus+0x2d/0xd0 ... Instead of relying on the component type to identify the upstream end of a link, use the "dev->has_secondary_link" field. This means it's now possible for an Upstream Port to have a link on its secondary side, so alloc_pcie_link_state() needs to connect links originating from both Upstream and Downstream Ports into the tree. [bhelgaas: changelog, add comment] Link: https://bugzilla.kernel.org/show_bug.cgi?id=94361 Link: http://lkml.kernel.org/r/54EB81B2.4050904@pobox.com Reported-by: Robert White <rwhite@pobox.com> Signed-off-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/pci/pcie/aspm.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 4e1af7637501..a84f87247d2f 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -525,7 +525,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
INIT_LIST_HEAD(&link->children);
INIT_LIST_HEAD(&link->link);
link->pdev = pdev;
- if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM) {
+ if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) {
struct pcie_link_state *parent;
parent = pdev->bus->parent->self->link_state;
if (!parent) {
@@ -559,10 +559,15 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
if (!aspm_support_enabled)
return;
- if (!pci_is_pcie(pdev) || pdev->link_state)
+ if (pdev->link_state)
return;
- if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
- pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM)
+
+ /*
+ * We allocate pcie_link_state for the component on the upstream
+ * end of a Link, so there's nothing to do unless this device has a
+ * Link on its secondary side.
+ */
+ if (!pdev->has_secondary_link)
return;
/* VIA has a strange chipset, root port is under a bridge */
@@ -715,8 +720,7 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
if (!pci_is_pcie(pdev))
return;
- if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
- pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM)
+ if (pdev->has_secondary_link)
parent = pdev;
if (!parent || !parent->link_state)
return;