| Message ID | 1375102331-23905-11-git-send-email-jeffrey.t.kirsher@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Mon, Jul 29, 2013 at 6:52 AM, Jeff Kirsher <jeffrey.t.kirsher@intel.com> wrote: > From: Jacob Keller <jacob.e.keller@intel.com> > > A PCI Express device can potentially report a link width and speed which it will > not properly fulfill due to being plugged into a slower link higher in the > chain. This function walks up the PCI bus chain and calculates the minimum link > width and speed of this entire chain. This can be useful to enable a device to > determine if it has enough bandwidth for optimum functionality. > > Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> > Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com> > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com> > --- > drivers/pci/pci.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > include/linux/pci.h | 2 ++ > 2 files changed, 45 insertions(+) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index e37fea6..c71e78c 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -3579,6 +3579,49 @@ int pcie_set_mps(struct pci_dev *dev, int mps) > } > > /** > + * pcie_get_minimum_link - determine minimum link settings of a PCI device > + * @dev: PCI device to query > + * @speed: storage for minimum speed > + * @width: storage for minimum width > + * > + * This function will walk up the PCI device chain and determine the minimum > + * link width and speed of the device. > + */ > +int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, > + enum pcie_link_width *width) > +{ > + int ret; > + > + *speed = PCI_SPEED_UNKNOWN; > + *width = PCIE_LNK_WIDTH_UNKNOWN; > + > + while (dev) { > + u16 lnksta; > + enum pci_bus_speed next_speed; > + enum pcie_link_width next_width; > + > + ret = pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta); > + if (ret) > + return ret; > + > + next_speed = pcie_link_speed[lnksta & PCI_EXP_LNKSTA_CLS]; > + next_width = (lnksta & PCI_EXP_LNKSTA_NLW) >> > + PCI_EXP_LNKSTA_NLW_SHIFT; > + > + if (next_speed < *speed) > + *speed = next_speed; > + > + if (next_width < *width) > + *width = next_width; > + > + dev = dev->bus->self; > + } > + > + return 0; > +} > +EXPORT_SYMBOL(pcie_get_minimum_link); > + > +/** > * pci_select_bars - Make BAR mask from the type of resource > * @dev: the PCI device for which BAR mask is made > * @flags: resource type mask to be selected > diff --git a/include/linux/pci.h b/include/linux/pci.h > index fc2d1fb..38994de 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -937,6 +937,8 @@ int pcie_get_readrq(struct pci_dev *dev); > int pcie_set_readrq(struct pci_dev *dev, int rq); > int pcie_get_mps(struct pci_dev *dev); > int pcie_set_mps(struct pci_dev *dev, int mps); > +int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, > + enum pcie_link_width *width); > int __pci_reset_function(struct pci_dev *dev); > int __pci_reset_function_locked(struct pci_dev *dev); > int pci_reset_function(struct pci_dev *dev); > -- > 1.7.11.7 > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index e37fea6..c71e78c 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3579,6 +3579,49 @@ int pcie_set_mps(struct pci_dev *dev, int mps) } /** + * pcie_get_minimum_link - determine minimum link settings of a PCI device + * @dev: PCI device to query + * @speed: storage for minimum speed + * @width: storage for minimum width + * + * This function will walk up the PCI device chain and determine the minimum + * link width and speed of the device. + */ +int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, + enum pcie_link_width *width) +{ + int ret; + + *speed = PCI_SPEED_UNKNOWN; + *width = PCIE_LNK_WIDTH_UNKNOWN; + + while (dev) { + u16 lnksta; + enum pci_bus_speed next_speed; + enum pcie_link_width next_width; + + ret = pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta); + if (ret) + return ret; + + next_speed = pcie_link_speed[lnksta & PCI_EXP_LNKSTA_CLS]; + next_width = (lnksta & PCI_EXP_LNKSTA_NLW) >> + PCI_EXP_LNKSTA_NLW_SHIFT; + + if (next_speed < *speed) + *speed = next_speed; + + if (next_width < *width) + *width = next_width; + + dev = dev->bus->self; + } + + return 0; +} +EXPORT_SYMBOL(pcie_get_minimum_link); + +/** * pci_select_bars - Make BAR mask from the type of resource * @dev: the PCI device for which BAR mask is made * @flags: resource type mask to be selected diff --git a/include/linux/pci.h b/include/linux/pci.h index fc2d1fb..38994de 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -937,6 +937,8 @@ int pcie_get_readrq(struct pci_dev *dev); int pcie_set_readrq(struct pci_dev *dev, int rq); int pcie_get_mps(struct pci_dev *dev); int pcie_set_mps(struct pci_dev *dev, int mps); +int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, + enum pcie_link_width *width); int __pci_reset_function(struct pci_dev *dev); int __pci_reset_function_locked(struct pci_dev *dev); int pci_reset_function(struct pci_dev *dev);