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[Tim Gardner <tim.gardner@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Xenial)
   Importance: Medium
       Status: Confirmed

** Changed in: linux (Ubuntu Xenial)
       Status: Confirmed => Fix Committed

** Changed in: linux (Ubuntu Xenial)
     Assignee: (unassigned) => Tim Gardner (timg-tpi)

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https://bugs.launchpad.net/bugs/1552627

Title:
  mlx4_en didn't choose time-stamping shift value according to HW
  frequency

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  Hi,

      Previously, the shift value used for time-stamping was constant and didn't
      depend on the HW chip frequency. Change that to take the frequency into account
      and calculate the maximal value in cycles per wraparound of ten seconds. This
      time slot was chosen since it gives a good accuracy in time synchronization.

      Algorithm for shift value calculation:
       * Round up the maximal value in cycles to nearest power of two

       * Calculate maximal multiplier by division of all 64 bits set
         to above result

       * Then, invert the function clocksource_khz2mult() to get the shift from
         maximal mult value


  below is the upstream commit that should fix the issue

  commit 31c128b66e5b28f468076e4f3ca3025c35342041

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