e1000e: 82574/82583 TimeSync errata for SYSTIM read

Due to a synchronization error, the value read from SYSTIML/SYSTIMH
might be incorrect.
Signed-off-by: Todd Fujinaka <todd.fujinaka@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/e1000.h

@@ -391,6 +391,8 @@ s32 e1000e_get_base_timinca(struct e1000_adapter *adapter, u32 *timinca);
  * 25MHz	46-bit	2^46 / 10^9 / 3600 = 19.55 hours
  */
 #define E1000_SYSTIM_OVERFLOW_PERIOD	(HZ * 60 * 60 * 4)
+#define E1000_MAX_82574_SYSTIM_REREADS	50
+#define E1000_82574_SYSTIM_EPSILON	(1ULL << 35ULL)
 
 /* hardware capability, feature, and workaround flags */
 #define FLAG_HAS_AMT                      (1 << 0)

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -4099,12 +4099,37 @@ static cycle_t e1000e_cyclecounter_read(const struct cyclecounter *cc)
 	struct e1000_adapter *adapter = container_of(cc, struct e1000_adapter,
 						     cc);
 	struct e1000_hw *hw = &adapter->hw;
-	cycle_t systim;
+	cycle_t systim, systim_next;
 
 	/* latch SYSTIMH on read of SYSTIML */
 	systim = (cycle_t)er32(SYSTIML);
 	systim |= (cycle_t)er32(SYSTIMH) << 32;
 
+	if ((hw->mac.type == e1000_82574) || (hw->mac.type == e1000_82583)) {
+		u64 incvalue, time_delta, rem, temp;
+		int i;
+
+		/* errata for 82574/82583 possible bad bits read from SYSTIMH/L
+		 * check to see that the time is incrementing at a reasonable
+		 * rate and is a multiple of incvalue
+		 */
+		incvalue = er32(TIMINCA) & E1000_TIMINCA_INCVALUE_MASK;
+		for (i = 0; i < E1000_MAX_82574_SYSTIM_REREADS; i++) {
+			/* latch SYSTIMH on read of SYSTIML */
+			systim_next = (cycle_t)er32(SYSTIML);
+			systim_next |= (cycle_t)er32(SYSTIMH) << 32;
+
+			time_delta = systim_next - systim;
+			temp = time_delta;
+			rem = do_div(temp, incvalue);
+
+			systim = systim_next;
+
+			if ((time_delta < E1000_82574_SYSTIM_EPSILON) &&
+			    (rem == 0))
+				break;
+		}
+	}
 	return systim;
 }