mainlining shenanigans
bf4bf09bdd
In the case where PTP is running on the hardware clock, but the kernel system time is not being synced, a device reset can mess up the clock time. This occurs because we reset the clock time based on the kernel time every reset. This causes us to potentially completely reset the PTP time, and can cause unexpected behavior in programs like ptp4l. Avoid this by saving the PTP time prior to device reset, and then restoring using that time after the reset. Directly restoring the PTP time we saved isn't perfect, because time should have continued running, but the clock will essentially be stopped during the reset. This is still better than the current solution of assuming that the PTP HW clock is synced to the CLOCK_REALTIME. We can do even better, by saving the ktime and calculating a differential, using ktime_get(). This is based on CLOCK_MONOTONIC, and allows us to get a fairly precise measure of the time difference between saving and restoring the time. Using this, we can update the saved PTP time, and use that as the value to write to the hardware clock registers. This, of course is not perfect. However, it does help ensure that the PTP time is restored as close as feasible to the time it should have been if the reset had not occurred. During device initialization, continue using the system time as the source for the creation of the PTP clock, since this is the best known current time source at driver load. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
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| Makefile | ||
| README | ||
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.