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The Rx timestamps reported by hardware may only have 32 bits of storage for nanosecond time. These timestamps cannot be directly reported to the Linux stack, as it expects 64bits of time. To handle this, the timestamps must be extended using an algorithm that calculates the corrected 64bit timestamp by comparison between the PHC time and the timestamp. This algorithm requires the PHC time to be captured within ~2 seconds of when the timestamp was captured. Instead of trying to read the PHC time in the Rx hotpath, the algorithm relies on a cached value that is periodically updated. Keep this cached time up to date by using the PTP .do_aux_work kthread function. The iavf_ptp_do_aux_work will reschedule itself about twice a second, and will check whether or not the cached PTP time needs to be updated. If so, it issues a VIRTCHNL_OP_1588_PTP_GET_TIME to request the time from the PF. The jitter and latency involved with this command aren't important, because the cached time just needs to be kept up to date within about ~2 seconds. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Simon Horman <horms@kernel.org> Tested-by: Rafal Romanowski <rafal.romanowski@intel.com> Co-developed-by: Mateusz Polchlopek <mateusz.polchlopek@intel.com> Signed-off-by: Mateusz Polchlopek <mateusz.polchlopek@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 reStructuredText 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.