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path: root/drivers/pci/pcie
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Diffstat (limited to 'drivers/pci/pcie')
-rw-r--r--drivers/pci/pcie/ptm.c22
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)