diff options
Diffstat (limited to 'drivers/pci/pcie/ptm.c')
| -rw-r--r-- | drivers/pci/pcie/ptm.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c index 9361f3aa26ab..357a454cafa0 100644 --- a/drivers/pci/pcie/ptm.c +++ b/drivers/pci/pcie/ptm.c @@ -39,10 +39,6 @@ void pci_ptm_init(struct pci_dev *dev) if (!pci_is_pcie(dev)) return; - pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM); - if (!pos) - return; - /* * Enable PTM only on interior devices (root ports, switch ports, * etc.) on the assumption that it causes no link traffic until an @@ -52,6 +48,23 @@ void pci_ptm_init(struct pci_dev *dev) pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END)) return; + /* + * Switch Downstream Ports are not permitted to have a PTM + * capability; their PTM behavior is controlled by the Upstream + * Port (PCIe r5.0, sec 7.9.16). + */ + ups = pci_upstream_bridge(dev); + if (pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM && + ups && ups->ptm_enabled) { + dev->ptm_granularity = ups->ptm_granularity; + dev->ptm_enabled = 1; + return; + } + + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM); + if (!pos) + return; + pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap); local_clock = (cap & PCI_PTM_GRANULARITY_MASK) >> 8; @@ -61,7 +74,6 @@ void pci_ptm_init(struct pci_dev *dev) * the spec recommendation (PCIe r3.1, sec 7.32.3), select the * furthest upstream Time Source as the PTM Root. */ - ups = pci_upstream_bridge(dev); if (ups && ups->ptm_enabled) { ctrl = PCI_PTM_CTRL_ENABLE; if (ups->ptm_granularity == 0) |