diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index ff1e72060952..91138cbeb853 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5146,6 +5146,64 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, } EXPORT_SYMBOL(pcie_get_minimum_link); +/** + * pcie_bandwidth_available - determine minimum link settings of a PCIe + * device and its bandwidth limitation + * @dev: PCI device to query + * @limiting_dev: storage for device causing the bandwidth limitation + * @speed: storage for speed of limiting device + * @width: storage for width of limiting device + * + * Walk up the PCI device chain and find the point where the minimum + * bandwidth is available. Return the bandwidth available there and (if + * limiting_dev, speed, and width pointers are supplied) information about + * that point. The bandwidth returned is in Mb/s, i.e., megabits/second of + * raw bandwidth. + */ +u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev, + enum pci_bus_speed *speed, + enum pcie_link_width *width) +{ + u16 lnksta; + enum pci_bus_speed next_speed; + enum pcie_link_width next_width; + u32 bw, next_bw; + + if (speed) + *speed = PCI_SPEED_UNKNOWN; + if (width) + *width = PCIE_LNK_WIDTH_UNKNOWN; + + bw = 0; + + while (dev) { + pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta); + + next_speed = pcie_link_speed[lnksta & PCI_EXP_LNKSTA_CLS]; + next_width = (lnksta & PCI_EXP_LNKSTA_NLW) >> + PCI_EXP_LNKSTA_NLW_SHIFT; + + next_bw = next_width * PCIE_SPEED2MBS_ENC(next_speed); + + /* Check if current device limits the total bandwidth */ + if (!bw || next_bw <= bw) { + bw = next_bw; + + if (limiting_dev) + *limiting_dev = dev; + if (speed) + *speed = next_speed; + if (width) + *width = next_width; + } + + dev = pci_upstream_bridge(dev); + } + + return bw; +} +EXPORT_SYMBOL(pcie_bandwidth_available); + /** * pcie_get_speed_cap - query for the PCI device's link speed capability * @dev: PCI device to query diff --git a/include/linux/pci.h b/include/linux/pci.h index 8043a5937ad0..f2bf2b7a66c7 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1083,6 +1083,9 @@ 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); +u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev, + enum pci_bus_speed *speed, + enum pcie_link_width *width); void pcie_flr(struct pci_dev *dev); int __pci_reset_function_locked(struct pci_dev *dev); int pci_reset_function(struct pci_dev *dev);