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>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 70d369e9139c..1d59ab6ca90f 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -586,7 +586,7 @@ struct i40e_pf {
 	unsigned long ptp_tx_start;
 	struct hwtstamp_config tstamp_config;
 	struct mutex tmreg_lock; /* Used to protect the SYSTIME registers. */
-	u64 ptp_base_adj;
+	u32 ptp_adj_mult;
 	u32 tx_hwtstamp_timeouts;
 	u32 tx_hwtstamp_skipped;
 	u32 rx_hwtstamp_cleared;