igb: serialize access to the time sync interrupt registers

The time sync related interrupt registers may be manipulated from
different contexts. This patch protects the registers from being
asynchronously changed by the reset function.

Also, the patch removes a misleading comment. The reset function
is disabling a bunch of functions, not enabling them.

Signed-off-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>

drivers/net/ethernet/intel/igb/igb_ptp.c

@@ -900,13 +900,16 @@ void igb_ptp_stop(struct igb_adapter *adapter)
 void igb_ptp_reset(struct igb_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
+	unsigned long flags;
 
 	if (!(adapter->flags & IGB_FLAG_PTP))
 		return;
 
 	/* reset the tstamp_config */
 	igb_ptp_set_timestamp_mode(adapter, &adapter->tstamp_config);
 
+	spin_lock_irqsave(&adapter->tmreg_lock, flags);
+
 	switch (adapter->hw.mac.type) {
 	case e1000_82576:
 		/* Dial the nominal frequency. */
@@ -917,23 +920,24 @@ void igb_ptp_reset(struct igb_adapter *adapter)
 	case e1000_i350:
 	case e1000_i210:
 	case e1000_i211:
-		/* Enable the timer functions and interrupts. */
 		wr32(E1000_TSAUXC, 0x0);
 		wr32(E1000_TSIM, TSYNC_INTERRUPTS);
 		wr32(E1000_IMS, E1000_IMS_TS);
 		break;
 	default:
 		/* No work to do. */
-		return;
+		goto out;
 	}
 
 	/* Re-initialize the timer. */
 	if ((hw->mac.type == e1000_i210) || (hw->mac.type == e1000_i211)) {
 		struct timespec ts = ktime_to_timespec(ktime_get_real());
 
-		igb_ptp_settime_i210(&adapter->ptp_caps, &ts);
+		igb_ptp_write_i210(adapter, &ts);
 	} else {
 		timecounter_init(&adapter->tc, &adapter->cc,
 				 ktime_to_ns(ktime_get_real()));
 	}
+out:
+	spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
 }