igb: Fix extts capture value format for 82580/i354/i350

82580/i354/i350 features circle-counter-like timestamp registers
that are different with newer i210. The EXTTS capture value in
AUXTSMPx should be converted from raw circle counter value to
timestamp value in resolution of 1 nanosec by the driver.

This issue can be reproduced on i350 nics, connecting an 1PPS
signal to a SDP pin, and run 'ts2phc' command to read external
1PPS timestamp value. On i210 this works fine, but on i350 the
extts is not correctly converted.

The i350/i354/82580's SYSTIM and other timestamp registers are
40bit counters, presenting time range of 2^40 ns, that means these
registers overflows every about 1099s. This causes all these regs
can't be used directly in contrast to the newer i210/i211s.

The igb driver needs to convert these raw register values to
valid time stamp format by using kernel timecounter apis for i350s
families. Here the igb_extts() just forgot to do the convert.

Fixes: 38970eac ("igb: support EXTTS on 82580/i354/i350")
Signed-off-by: Yuezhen Luan <eggcar.luan@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230607164116.3768175-1-anthony.l.nguyen@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -6947,6 +6947,7 @@ static void igb_extts(struct igb_adapter *adapter, int tsintr_tt)
 	struct e1000_hw *hw = &adapter->hw;
 	struct ptp_clock_event event;
 	struct timespec64 ts;
+	unsigned long flags;
 
 	if (pin < 0 || pin >= IGB_N_SDP)
 		return;
@@ -6954,9 +6955,12 @@ static void igb_extts(struct igb_adapter *adapter, int tsintr_tt)
 	if (hw->mac.type == e1000_82580 ||
 	    hw->mac.type == e1000_i354 ||
 	    hw->mac.type == e1000_i350) {
-		s64 ns = rd32(auxstmpl);
+		u64 ns = rd32(auxstmpl);
 
-		ns += ((s64)(rd32(auxstmph) & 0xFF)) << 32;
+		ns += ((u64)(rd32(auxstmph) & 0xFF)) << 32;
+		spin_lock_irqsave(&adapter->tmreg_lock, flags);
+		ns = timecounter_cyc2time(&adapter->tc, ns);
+		spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
 		ts = ns_to_timespec64(ns);
 	} else {
 		ts.tv_nsec = rd32(auxstmpl);