From: Wojciech Drewek <[email protected]> Date: Wed, 21 Aug 2024 14:15:33 +0200
> From: Jacob Keller <[email protected]> > > 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 <[email protected]> > Reviewed-by: Wojciech Drewek <[email protected]> > Reviewed-by: Simon Horman <[email protected]> > Co-developed-by: Mateusz Polchlopek <[email protected]> > Signed-off-by: Mateusz Polchlopek <[email protected]> > Signed-off-by: Wojciech Drewek <[email protected]> > --- > drivers/net/ethernet/intel/iavf/iavf_ptp.c | 52 ++++++++++++++++++++++ > drivers/net/ethernet/intel/iavf/iavf_ptp.h | 1 + > 2 files changed, 53 insertions(+) > > diff --git a/drivers/net/ethernet/intel/iavf/iavf_ptp.c > b/drivers/net/ethernet/intel/iavf/iavf_ptp.c > index d709d381958f..7124a717cd03 100644 > --- a/drivers/net/ethernet/intel/iavf/iavf_ptp.c > +++ b/drivers/net/ethernet/intel/iavf/iavf_ptp.c > @@ -153,6 +153,55 @@ static int iavf_ptp_gettimex64(struct ptp_clock_info > *info, > return iavf_read_phc_indirect(adapter, ts, sts); > } > > +/** > + * iavf_ptp_cache_phc_time - Cache PHC time for performing timestamp > extension > + * @adapter: private adapter structure > + * > + * Periodically cache the PHC time in order to allow for timestamp extension. > + * This is required because the Tx and Rx timestamps only contain 32bits of > + * nanoseconds. Timestamp extension allows calculating the corrected 64bit > + * timestamp. This algorithm relies on the cached time being within ~1 second > + * of the timestamp. > + */ > +static void iavf_ptp_cache_phc_time(struct iavf_adapter *adapter) > +{ > + if (time_is_before_jiffies(adapter->ptp.cached_phc_updated + HZ)) { Also invert the condition to avoid +1 indent level? > + /* The response from virtchnl will store the time into > + * cached_phc_time. > + */ > + iavf_send_phc_read(adapter); > + } > +} > + > +/** > + * iavf_ptp_do_aux_work - Perform periodic work required for PTP support > + * @info: PTP clock info structure > + * > + * Handler to take care of periodic work required for PTP operation. This > + * includes the following tasks: > + * > + * 1) updating cached_phc_time > + * > + * cached_phc_time is used by the Tx and Rx timestamp flows in order to > + * perform timestamp extension, by carefully comparing the timestamp > + * 32bit nanosecond timestamps and determining the corrected 64bit > + * timestamp value to report to userspace. This algorithm only works if > + * the cached_phc_time is within ~1 second of the Tx or Rx timestamp > + * event. This task periodically reads the PHC time and stores it, to > + * ensure that timestamp extension operates correctly. > + * > + * Returns: time in jiffies until the periodic task should be re-scheduled. > + */ > +long iavf_ptp_do_aux_work(struct ptp_clock_info *info) Why isn't it static since it's used only within this one file? > +{ > + struct iavf_adapter *adapter = iavf_clock_to_adapter(info); > + > + iavf_ptp_cache_phc_time(adapter); > + > + /* Check work about twice a second */ > + return msecs_to_jiffies(500); Thanks, Olek
