On Wed, Jul 5, 2017 at 9:19 PM, Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote: > According to extended tags ECN document, all PCIe receivers are expected > to support extended tags support. It should be safe to enable extended > tags on endpoints without checking compatibility. > > This assumption seems to be working fine except for the legacy systems. > The ECN has been written against PCIE spec version 2.0. Therefore, we need > to exclude all version 1.0 devices from this change as there is HW out > there that can't handle extended tags. > > Note that the default value of Extended Tags Enable bit is implementation > specific. Therefore, we are clearing the bit by default when incompatible > HW is found without assuming that value is zero. > > Reported-by: Wim ten Have <wim.ten.have@xxxxxxxxxx> > Link: https://pcisig.com/sites/default/files/specification_documents/ECN_Extended_Tag_Enable_Default_05Sept2008_final.pdf > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1467674 > Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported") > Tested-by: Wim ten Have <wim.ten.have@xxxxxxxxxx> > Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx> > --- > drivers/pci/probe.c | 52 +++++++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 45 insertions(+), 7 deletions(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 19c8950..5e39013 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -1684,21 +1684,58 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp) > */ > } > > -static void pci_configure_extended_tags(struct pci_dev *dev) > +static bool pcie_bus_exttags_supported(struct pci_bus *bus) > +{ > + bool exttags_supported = true; > + struct pci_dev *bridge; > + int rc; > + u16 flags; > + > + bridge = bus->self; > + while (bridge) { > + if (pci_is_pcie(bridge)) { > + rc = pcie_capability_read_word(bridge, PCI_EXP_FLAGS, > + &flags); > + if (!rc && ((flags & PCI_EXP_FLAGS_VERS) < 2)) { > + exttags_supported = false; > + break; > + } > + } > + if (!bridge->bus->parent) > + break; > + bridge = bridge->bus->parent->self; > + } > + > + return exttags_supported; > +} > + > +static int pcie_bus_configure_exttags(struct pci_dev *dev, void *data) > { > u32 dev_cap; > int ret; > + bool supported; > > if (!pci_is_pcie(dev)) > - return; > + return 0; > > ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &dev_cap); > if (ret) > - return; > + return 0; > > - if (dev_cap & PCI_EXP_DEVCAP_EXT_TAG) > - pcie_capability_set_word(dev, PCI_EXP_DEVCTL, > - PCI_EXP_DEVCTL_EXT_TAG); > + if (dev_cap & PCI_EXP_DEVCAP_EXT_TAG) { > + supported = pcie_bus_exttags_supported(dev->bus); > + Maybe checking the version of this endpoint at first? Do you expect a v1 endpoint to be working under v2+ ports? -- Thanks, Jike
