The PTM Control register (PCIe r3.1, sec 7.32.3) contains an Effective
Granularity field:
This provides information relating to the expected accuracy of the PTM
clock, but does not otherwise affect the PTM mechanism.
Set the Effective Granularity based on the PTM Root and any intervening PTM
Time Sources.
This does not set Effective Granularity for Root Complex Integrated
Endpoints because I don't know how to figure out clock granularity for
them. The spec says:
... system software must set [Effective Granularity] to the value
reported in the Local Clock Granularity field by the associated PTM
Time Source.
but I don't know how to identify the associated PTM Time Source. Normally
it's the upstream bridge, but an integrated endpoint has no upstream
bridge.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Add an pci_enable_ptm() interface so drivers can enable PTM.
The PCI core enables PTM on PTM Roots and switches automatically, but we
don't enable PTM on endpoints unless a driver requests it.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Add Precision Time Measurement (PTM) support (see PCIe r3.1, sec 6.22).
Enable PTM on PTM Root devices and switch ports. This does not enable PTM
on endpoints.
There currently are no PTM-capable devices on the market, but it is
expected to be supported by the Intel Apollo Lake platform.
[bhelgaas: complete rework]
Signed-off-by: Jonathan Yong <jonathan.yong@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Bjorn Helgaas
Jonathan Yong