On 03/23/2016 12:04, Yong, Jonathan wrote:
Hello LKML, This is a preliminary implementation of the PTM[1] support driver, the code is obviously hacked together and in need of refactoring. This driver has only been tested against a virtual PCI bus. The drivers job is to get to every PTM capable device, set some PCI config space bits, then go back to sleep [2]. PTM capable PCIe devices will get a new sysfs entry to allow PTM to be enabled if automatic PTM activation is disabled, or disabled if so desired. Comments? Should I explain the PTM registers in more details? Please CC me, thanks. [1] Precision Time Measurement: A protocol for synchronizing PCIe endpoint clocks against the host clock as specified in the PCI Express Base Specification 3.1. It is identified by the 0x001f extended capability ID. PTM capable devices are split into 3 roles, master, responder and requester. Summary as follows: A master holds the master clock that will be used for all devices under its domain (not to be confused with PCI domains). There may be multiple masters in a PTM hierarchy, in which case, the highest master closest to the root complex will be selected for the PTM domain. A master is also always responder capable. Clock precision is signified by a Local Clock Granularity field, in nano-seconds. A responder responds to any PTM synchronization requests from a downstream device. A responder is typically a switch device. It may also hold a local clock signified by a non-zero Local Clock Granularity field. A value of 0 signifies that the device simply propagates timing information from upstream devices. A requester is typically an endpoint that will request synchronization updates from an upstream PTM capable time source. The driver will update the Effective Clock Granularity field based on the same field from the PTM domain master. The field should be programmed with a value of 0 if any intervening responder has a Local Clock Granularity field value of 0. [2] The software drivers never see the PTM packets, the PCI Express Base Specification 3.1 reads: PTM capable components can make their PTM context available for inspection by software, enabling software to translate timing information between local times and PTM Master Time. This isn't very informative. Changes since v1: * Moved register constants to pci_regs.h * Use pci_dev to hold PTM status * PTM initialization now done top-down hierarchy wise. Changes since v2: * Added missing void return in the pci_ptm_init inline stub. Yong, Jonathan (1): PCI: PTM preliminary implementation drivers/pci/pci-sysfs.c | 7 ++ drivers/pci/pci.h | 25 +++++ drivers/pci/pcie/Kconfig | 8 ++ drivers/pci/pcie/Makefile | 2 +- drivers/pci/pcie/pcie_ptm.c | 212 ++++++++++++++++++++++++++++++++++++++++++ drivers/pci/probe.c | 3 + include/linux/pci.h | 9 ++ include/uapi/linux/pci_regs.h | 12 +++ 8 files changed, 277 insertions(+), 1 deletion(-) create mode 100644 drivers/pci/pcie/pcie_ptm.c
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