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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 500462a9de ("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.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Acked-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
hifive-unleashed-5.1
Miroslav Lichvar 2018-10-26 19:13:00 +02:00 committed by Jeff Kirsher
parent d944b46992
commit 4c9b658eea
1 changed files with 7 additions and 5 deletions
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12
drivers/net/ethernet/intel/igb/igb_ptp.c
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@ -53,13 +53,15 @@
* 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, so we aim for 8
* minutes to be sure the actual interval is shorter than 9.16 minutes.
* 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 * 8)
#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)