igc: move ktime snapshot into PTM retry loop

[ Upstream commit cd7f7328d691937102732f39f97ead35b15bf803 ]

Move ktime_get_snapshot() into the loop. If a retry does occur, a more
recent snapshot will result in a more accurate cross-timestamp.

Fixes: a90ec84 ("igc: Add support for PTP getcrosststamp()")
Reviewed-by: Michal Swiatkowski <[email protected]>
Tested-by: Mor Bar-Gabay <[email protected]>
Tested-by: Avigail Dahan <[email protected]>
Signed-off-by: Christopher S M Hall <[email protected]>
Reviewed-by: Corinna Vinschen <[email protected]>
Signed-off-by: Jacob Keller <[email protected]>
Acked-by: Vinicius Costa Gomes <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
(cherry picked from commit 8058c895c7c6921601edf906d0560c1bec9d077a)
Signed-off-by: Jack Vogel <[email protected]>

Author: christopher-s-hall

drivers/net/ethernet/intel/igc/igc_ptp.c

@@ -1011,16 +1011,16 @@ static int igc_phc_get_syncdevicetime(ktime_t *device,
 	int err, count = 100;
 	ktime_t t1, t2_curr;
 
-	/* Get a snapshot of system clocks to use as historic value. */
-	ktime_get_snapshot(&adapter->snapshot);
-
+	/* Doing this in a loop because in the event of a
+	 * badly timed (ha!) system clock adjustment, we may
+	 * get PTM errors from the PCI root, but these errors
+	 * are transitory. Repeating the process returns valid
+	 * data eventually.
+	 */
 	do {
-		/* Doing this in a loop because in the event of a
-		 * badly timed (ha!) system clock adjustment, we may
-		 * get PTM errors from the PCI root, but these errors
-		 * are transitory. Repeating the process returns valid
-		 * data eventually.
-		 */
+		/* Get a snapshot of system clocks to use as historic value. */
+		ktime_get_snapshot(&adapter->snapshot);
+
 		igc_ptm_trigger(hw);
 
 		err = readx_poll_timeout(rd32, IGC_PTM_STAT, stat,