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PCI/PTM: Inherit Switch Downstream Port PTM settings from Upstream Port 

Except for Endpoints, we enable PTM at enumeration-time.  Previously we did
not account for the fact that 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).  Since Downstream Ports don't have a PTM
capability, we did not mark them as "ptm_enabled", which meant that
pci_enable_ptm() on an Endpoint failed because there was no PTM path to it.

Mark Downstream Ports as "ptm_enabled" if their Upstream Port has PTM
enabled.

Fixes: eec097d431 ("PCI: Add pci_enable_ptm() for drivers to enable PTM on endpoints")
Reported-by: Aditya Paluri <Venkata.AdityaPaluri@synopsys.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Bjorn Helgaas 2020-05-21 15:40:07 -05:00
parent aa0ce96d72
commit 7b38fd9760
1 changed files with 17 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/pci/pcie/ptm.c
View File

@ -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)