iavf: periodically cache PHC time

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>

0 files changed, 0 insertions, 0 deletions