> -----Original Message----- > From: Miroslav Lichvar [mailto:mlich...@redhat.com] > Sent: Friday, October 26, 2018 10:13 AM > To: netdev@vger.kernel.org > Cc: intel-wired-...@lists.osuosl.org; Miroslav Lichvar <mlich...@redhat.com>; > Keller, Jacob E <jacob.e.kel...@intel.com>; Richard Cochran > <richardcoch...@gmail.com>; Thomas Gleixner <t...@linutronix.de> > Subject: [PATCH v2 net] igb: shorten maximum PHC timecounter update interval > > The timecounter needs to be updated at least once per ~550 seconds in > order to avoid a 40-bit SYSTIM timestamp to be misinterpreted as an old > timestamp. > > Since commit 500462a9de65 ("timers: Switch to a non-cascading wheel"), > scheduling of delayed work seems to be less accurate and a requested > delay of 540 seconds may actually be longer than 550 seconds. Also, the > PHC may be adjusted to run up to 6% faster than real time and the system > clock up to 10% slower. Shorten the delay to 360 seconds to be sure the > timecounter is updated in time. > > This fixes an issue with HW timestamps on 82580/I350/I354 being off by > ~1100 seconds for few seconds every ~9 minutes. >
Acked-by: Jacob Keller <jacob.e.kel...@intel.com> > Cc: Jacob Keller <jacob.e.kel...@intel.com> > Cc: Richard Cochran <richardcoch...@gmail.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Signed-off-by: Miroslav Lichvar <mlich...@redhat.com> > --- > drivers/net/ethernet/intel/igb/igb_ptp.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c > b/drivers/net/ethernet/intel/igb/igb_ptp.c > index 9f4d700e09df..2b95dc9c7a6a 100644 > --- a/drivers/net/ethernet/intel/igb/igb_ptp.c > +++ b/drivers/net/ethernet/intel/igb/igb_ptp.c > @@ -51,9 +51,17 @@ > * > * The 40 bit 82580 SYSTIM overflows every > * 2^40 * 10^-9 / 60 = 18.3 minutes. > + * > + * SYSTIM is converted to real time using a timecounter. As > + * timecounter_cyc2time() allows old timestamps, the timecounter needs > + * to be updated at least once per half of the SYSTIM interval. > + * Scheduling of delayed work is not very accurate, and also the NIC > + * clock can be adjusted to run up to 6% faster and the system clock > + * up to 10% slower, so we aim for 6 minutes to be sure the actual > + * interval in the NIC time is shorter than 9.16 minutes. > */ > > -#define IGB_SYSTIM_OVERFLOW_PERIOD (HZ * 60 * 9) > +#define IGB_SYSTIM_OVERFLOW_PERIOD (HZ * 60 * 6) > #define IGB_PTP_TX_TIMEOUT (HZ * 15) > #define INCPERIOD_82576 BIT(E1000_TIMINCA_16NS_SHIFT) > #define INCVALUE_82576_MASK > GENMASK(E1000_TIMINCA_16NS_SHIFT - 1, 0) > -- > 2.17.2
