On Tue, May 19, 2015 at 11:26:45AM +0800, Yijing Wang wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=94361 reported > in ATCA platform, system had unusual pcie topology: > > (root port) (downstream port) (upstream port) > +-1c.0-[02-0a]----00.0-[03-0a]--+-00.0-[04]-- > | +-01.0-[05]-- (downstream port) > | +-02.0-[06]-- > | +-03.0-[07]-- > | +-08.0-[08]-- > | +-09.0-[09]-- > | \-0a.0-[0a]-- > We assumed root port and downstream port always > have external link, and downstream port always has a > upstream port. So in this case, when we allocated > pcie_link_state for downstream port 02:00.0, it try > to get parent bus pcie_link_state, > parent = pdev->bus->parent->self->link_state; > because root bus self is NULL, system will crash here. > > This patch fix this issue based on the following > assumption suggested by Bjorn. > 1. Root port is always on the upstream end of a link. > 2. The pcie hierarchy should alternate between links > and internal switch logic, there should be no adjacent > links or internal buses in pcie tree. > > Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx> > --- > drivers/pci/pcie/aspm.c | 7 +++---- > drivers/pci/probe.c | 12 ++++++++++++ > include/linux/pci.h | 1 + > 3 files changed, 16 insertions(+), 4 deletions(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index 7d4fcdc..8830740 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -561,8 +561,8 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev) > > if (!pci_is_pcie(pdev) || pdev->link_state) > return; > - if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT && > - pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM) > + > + if (!pdev->has_secondary_link) > return; > > /* VIA has a strange chipset, root port is under a bridge */ > @@ -723,8 +723,7 @@ 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; Can you separate the ASPM part from the addition of pdev->has_secondary_link? I think there will be other users, and I don't necessarily want the patch to suggest that it's only needed for ASPM. > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index a9c5e63..ad26ff2 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -982,6 +982,18 @@ void set_pcie_port_type(struct pci_dev *pdev) > pdev->pcie_flags_reg = reg16; > pci_read_config_word(pdev, pos + PCI_EXP_DEVCAP, ®16); > pdev->pcie_mpss = reg16 & PCI_EXP_DEVCAP_PAYLOAD; > + > + /* > + * We assume root port is always on the upstream end of > + * a link, and the pcie hierarchy should alternate > + * between links and internal switch logic. > + */ > + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT) > + pdev->has_secondary_link = 1; > + > + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM > + && !pdev->bus->self->has_secondary_link) Please use pci_upstream_bridge() here instead of chasing the pointers explicitly. Then we don't have to worry about whether any of the corner cases handled in pci_upstream_bridge() apply here. The fact that you only set has_secondary_link for Downstream Ports means we won't handle the case of Upstream Ports (device 03:00.0 in this topology). That port *does* have a link on its secondary side. Is there a reason you want to exclude it? It seems like we ought to be able to enable ASPM on that link. > + pdev->has_secondary_link = 1; > } > > void set_pcie_hotplug_bridge(struct pci_dev *pdev) > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 50b7c7d..141fcc1 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -355,6 +355,7 @@ struct pci_dev { > unsigned int broken_intx_masking:1; > unsigned int io_window_1k:1; /* Intel P2P bridge 1K I/O windows */ > unsigned int irq_managed:1; > + unsigned int has_secondary_link:1; > pci_dev_flags_t dev_flags; > atomic_t enable_cnt; /* pci_enable_device has been called */ > > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
