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Mainline Linux tree for various devices, only for fun :)
a90ec84837
i225 supports PCIe Precision Time Measurement (PTM), allowing us to support the PTP_SYS_OFFSET_PRECISE ioctl() in the driver via the getcrosststamp() function. The easiest way to expose the PTM registers would be to configure the PTM dialogs to run periodically, but the PTP_SYS_OFFSET_PRECISE ioctl() semantics are more aligned to using a kind of "one-shot" way of retrieving the PTM timestamps. But this causes a bit more code to be written: the trigger registers for the PTM dialogs are not cleared automatically. i225 can be configured to send "fake" packets with the PTM information, adding support for handling these types of packets is left for the future. PTM improves the accuracy of time synchronization, for example, using phc2sys, while a simple application is sending packets as fast as possible. First, without .getcrosststamp(): phc2sys[191.382]: enp4s0 sys offset -959 s2 freq -454 delay 4492 phc2sys[191.482]: enp4s0 sys offset 798 s2 freq +1015 delay 4069 phc2sys[191.583]: enp4s0 sys offset 962 s2 freq +1418 delay 3849 phc2sys[191.683]: enp4s0 sys offset 924 s2 freq +1669 delay 3753 phc2sys[191.783]: enp4s0 sys offset 664 s2 freq +1686 delay 3349 phc2sys[191.883]: enp4s0 sys offset 218 s2 freq +1439 delay 2585 phc2sys[191.983]: enp4s0 sys offset 761 s2 freq +2048 delay 3750 phc2sys[192.083]: enp4s0 sys offset 756 s2 freq +2271 delay 4061 phc2sys[192.183]: enp4s0 sys offset 809 s2 freq +2551 delay 4384 phc2sys[192.283]: enp4s0 sys offset -108 s2 freq +1877 delay 2480 phc2sys[192.383]: enp4s0 sys offset -1145 s2 freq +807 delay 4438 phc2sys[192.484]: enp4s0 sys offset 571 s2 freq +2180 delay 3849 phc2sys[192.584]: enp4s0 sys offset 241 s2 freq +2021 delay 3389 phc2sys[192.684]: enp4s0 sys offset 405 s2 freq +2257 delay 3829 phc2sys[192.784]: enp4s0 sys offset 17 s2 freq +1991 delay 3273 phc2sys[192.884]: enp4s0 sys offset 152 s2 freq +2131 delay 3948 phc2sys[192.984]: enp4s0 sys offset -187 s2 freq +1837 delay 3162 phc2sys[193.084]: enp4s0 sys offset -1595 s2 freq +373 delay 4557 phc2sys[193.184]: enp4s0 sys offset 107 s2 freq +1597 delay 3740 phc2sys[193.284]: enp4s0 sys offset 199 s2 freq +1721 delay 4010 phc2sys[193.385]: enp4s0 sys offset -169 s2 freq +1413 delay 3701 phc2sys[193.485]: enp4s0 sys offset -47 s2 freq +1484 delay 3581 phc2sys[193.585]: enp4s0 sys offset -65 s2 freq +1452 delay 3778 phc2sys[193.685]: enp4s0 sys offset 95 s2 freq +1592 delay 3888 phc2sys[193.785]: enp4s0 sys offset 206 s2 freq +1732 delay 4445 phc2sys[193.885]: enp4s0 sys offset -652 s2 freq +936 delay 2521 phc2sys[193.985]: enp4s0 sys offset -203 s2 freq +1189 delay 3391 phc2sys[194.085]: enp4s0 sys offset -376 s2 freq +955 delay 2951 phc2sys[194.185]: enp4s0 sys offset -134 s2 freq +1084 delay 3330 phc2sys[194.285]: enp4s0 sys offset -22 s2 freq +1156 delay 3479 phc2sys[194.386]: enp4s0 sys offset 32 s2 freq +1204 delay 3602 phc2sys[194.486]: enp4s0 sys offset 122 s2 freq +1303 delay 3731 Statistics for this run (total of 2179 lines), in nanoseconds: average: -1.12 stdev: 634.80 max: 1551 min: -2215 With .getcrosststamp() via PCIe PTM: phc2sys[367.859]: enp4s0 sys offset 6 s2 freq +1727 delay 0 phc2sys[367.959]: enp4s0 sys offset -2 s2 freq +1721 delay 0 phc2sys[368.059]: enp4s0 sys offset 5 s2 freq +1727 delay 0 phc2sys[368.160]: enp4s0 sys offset -1 s2 freq +1723 delay 0 phc2sys[368.260]: enp4s0 sys offset -4 s2 freq +1719 delay 0 phc2sys[368.360]: enp4s0 sys offset -5 s2 freq +1717 delay 0 phc2sys[368.460]: enp4s0 sys offset 1 s2 freq +1722 delay 0 phc2sys[368.560]: enp4s0 sys offset -3 s2 freq +1718 delay 0 phc2sys[368.660]: enp4s0 sys offset 5 s2 freq +1725 delay 0 phc2sys[368.760]: enp4s0 sys offset -1 s2 freq +1721 delay 0 phc2sys[368.860]: enp4s0 sys offset 0 s2 freq +1721 delay 0 phc2sys[368.960]: enp4s0 sys offset 0 s2 freq +1721 delay 0 phc2sys[369.061]: enp4s0 sys offset 4 s2 freq +1725 delay 0 phc2sys[369.161]: enp4s0 sys offset 1 s2 freq +1724 delay 0 phc2sys[369.261]: enp4s0 sys offset 4 s2 freq +1727 delay 0 phc2sys[369.361]: enp4s0 sys offset 8 s2 freq +1732 delay 0 phc2sys[369.461]: enp4s0 sys offset 7 s2 freq +1733 delay 0 phc2sys[369.561]: enp4s0 sys offset 4 s2 freq +1733 delay 0 phc2sys[369.661]: enp4s0 sys offset 1 s2 freq +1731 delay 0 phc2sys[369.761]: enp4s0 sys offset 1 s2 freq +1731 delay 0 phc2sys[369.861]: enp4s0 sys offset -5 s2 freq +1725 delay 0 phc2sys[369.961]: enp4s0 sys offset -4 s2 freq +1725 delay 0 phc2sys[370.062]: enp4s0 sys offset 2 s2 freq +1730 delay 0 phc2sys[370.162]: enp4s0 sys offset -7 s2 freq +1721 delay 0 phc2sys[370.262]: enp4s0 sys offset -3 s2 freq +1723 delay 0 phc2sys[370.362]: enp4s0 sys offset 1 s2 freq +1726 delay 0 phc2sys[370.462]: enp4s0 sys offset -3 s2 freq +1723 delay 0 phc2sys[370.562]: enp4s0 sys offset -1 s2 freq +1724 delay 0 phc2sys[370.662]: enp4s0 sys offset -4 s2 freq +1720 delay 0 phc2sys[370.762]: enp4s0 sys offset -7 s2 freq +1716 delay 0 phc2sys[370.862]: enp4s0 sys offset -2 s2 freq +1719 delay 0 Statistics for this run (total of 2179 lines), in nanoseconds: average: 0.14 stdev: 5.03 max: 48 min: -27 For reference, the statistics for runs without PCIe congestion show that the improvements from enabling PTM are less dramatic. For two runs of 16466 entries: without PTM: avg -0.04 stdev 10.57 max 39 min -42 with PTM: avg 0.01 stdev 4.20 max 19 min -16 One possible explanation is that when PTM is not enabled, and there's a lot of traffic in the PCIe fabric, some register reads will take more time than the others because of congestion on the PCIe fabric. When PTM is enabled, even if the PTM dialogs take more time to complete under heavy traffic, the time measurements do not depend on the time to read the registers. This was implemented following the i225 EAS version 0.993. Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com> Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.