igb: Avoid starting unnecessary workqueues

[ Upstream commit b888c510f7b3d64ca75fc0f43b4a4bd1a611312f ]

If ptp_clock_register() fails or CONFIG_PTP isn't enabled, avoid starting
PTP related workqueues.

In this way we can fix this:
 BUG: unable to handle page fault for address: ffffc9000440b6f8
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 100000067 P4D 100000067 PUD 1001e0067 PMD 107dc5067 PTE 0
 Oops: 0000 [whatawurst#1] PREEMPT SMP
 [...]
 Workqueue: events igb_ptp_overflow_check
 RIP: 0010:igb_rd32+0x1f/0x60
 [...]
 Call Trace:
  igb_ptp_read_82580+0x20/0x50
  timecounter_read+0x15/0x60
  igb_ptp_overflow_check+0x1a/0x50
  process_one_work+0x1cb/0x3c0
  worker_thread+0x53/0x3f0
  ? rescuer_thread+0x370/0x370
  kthread+0x142/0x160
  ? kthread_associate_blkcg+0xc0/0xc0
  ret_from_fork+0x1f/0x30

Fixes: 1f6e817 ("igb: Prevent dropped Tx timestamps via work items and interrupts.")
Fixes: d339b13 ("igb: add PTP Hardware Clock code")
Signed-off-by: Alessio Igor Bogani <alessio.bogani@elettra.eu>
Tested-by: Arpana Arland <arpanax.arland@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230821171927.2203644-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[uli: backport to 4.4]
Signed-off-by: Ulrich Hecht <uli@kernel.org>

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

@@ -1089,34 +1089,6 @@ void igb_ptp_init(struct igb_adapter *adapter)
 
 	wrfl();
 
-	spin_lock_init(&adapter->tmreg_lock);
-	INIT_WORK(&adapter->ptp_tx_work, igb_ptp_tx_work);
-
-	/* Initialize the clock and overflow work for devices that need it. */
-	if ((hw->mac.type == e1000_i210) || (hw->mac.type == e1000_i211)) {
-		struct timespec64 ts = ktime_to_timespec64(ktime_get_real());
-
-		igb_ptp_settime_i210(&adapter->ptp_caps, &ts);
-	} else {
-		timecounter_init(&adapter->tc, &adapter->cc,
-				 ktime_to_ns(ktime_get_real()));
-
-		INIT_DELAYED_WORK(&adapter->ptp_overflow_work,
-				  igb_ptp_overflow_check);
-
-		schedule_delayed_work(&adapter->ptp_overflow_work,
-				      IGB_SYSTIM_OVERFLOW_PERIOD);
-	}
-
-	/* Initialize the time sync interrupts for devices that support it. */
-	if (hw->mac.type >= e1000_82580) {
-		wr32(E1000_TSIM, TSYNC_INTERRUPTS);
-		wr32(E1000_IMS, E1000_IMS_TS);
-	}
-
-	adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
-	adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
-
 	adapter->ptp_clock = ptp_clock_register(&adapter->ptp_caps,
 						&adapter->pdev->dev);
 	if (IS_ERR(adapter->ptp_clock)) {
@@ -1126,6 +1098,34 @@ void igb_ptp_init(struct igb_adapter *adapter)
 		dev_info(&adapter->pdev->dev, "added PHC on %s\n",
 			 adapter->netdev->name);
 		adapter->flags |= IGB_FLAG_PTP;
+
+		spin_lock_init(&adapter->tmreg_lock);
+		INIT_WORK(&adapter->ptp_tx_work, igb_ptp_tx_work);
+
+		/* Initialize the clock and overflow work for devices that need it. */
+		if ((hw->mac.type == e1000_i210) || (hw->mac.type == e1000_i211)) {
+			struct timespec64 ts = ktime_to_timespec64(ktime_get_real());
+
+			igb_ptp_settime_i210(&adapter->ptp_caps, &ts);
+		} else {
+			timecounter_init(&adapter->tc, &adapter->cc,
+					 ktime_to_ns(ktime_get_real()));
+
+			INIT_DELAYED_WORK(&adapter->ptp_overflow_work,
+					  igb_ptp_overflow_check);
+
+			schedule_delayed_work(&adapter->ptp_overflow_work,
+					      IGB_SYSTIM_OVERFLOW_PERIOD);
+		}
+
+		/* Initialize the time sync interrupts for devices that support it. */
+		if (hw->mac.type >= e1000_82580) {
+			wr32(E1000_TSIM, TSYNC_INTERRUPTS);
+			wr32(E1000_IMS, E1000_IMS_TS);
+		}
+
+		adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
+		adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
 	}
 }