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i40e: avoid overflow in i40e_ptp_adjfreq()
When operating at 1GbE, the base incval for the PTP clock is so large that multiplying it by numbers close to the max_adj can overflow the u64. Rather than attempting to limit the max_adj to a value small enough to avoid overflow, instead calculate the incvalue adjustment based on the 40GbE incvalue, and then multiply that by the scaling factor for the link speed. This sacrifices a small amount of precision in the adjustment but we avoid erratic behavior of the clock due to the overflow caused if ppb is very near the maximum adjustment. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Tested-by: Andrew Bowers <andrewx.bowers@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Jacob Keller
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Jeff Kirsher
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Apr 30, 2018
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