igc: fix page fault when thunderbolt is unplugged

After unplug thunderbolt dock with i225, pciehp interrupt is triggered,
remove call will read/write mmio address which is already disconnected,
then cause page fault and make system hang.

Check PCI state to remove device safely.

Trace:
BUG: unable to handle page fault for address: 000000000000b604
Oops: 0000 [#1] SMP NOPTI
RIP: 0010:igc_rd32+0x1c/0x90 [igc]
Call Trace:
igc_ptp_suspend+0x6c/0xa0 [igc]
igc_ptp_stop+0x12/0x50 [igc]
igc_remove+0x7f/0x1c0 [igc]
pci_device_remove+0x3e/0xb0
__device_release_driver+0x181/0x240

Fixes: 13b5b7fd ("igc: Add support for Tx/Rx rings")
Fixes: b03c49cd ("igc: Save PTP time before a reset")
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

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

@@ -149,6 +149,9 @@ static void igc_release_hw_control(struct igc_adapter *adapter)
 	struct igc_hw *hw = &adapter->hw;
 	u32 ctrl_ext;
 
+	if (!pci_device_is_present(adapter->pdev))
+		return;
+
 	/* Let firmware take over control of h/w */
 	ctrl_ext = rd32(IGC_CTRL_EXT);
 	wr32(IGC_CTRL_EXT,
@@ -4449,26 +4452,29 @@ void igc_down(struct igc_adapter *adapter)
 
 	igc_ptp_suspend(adapter);
 
-	/* disable receives in the hardware */
-	rctl = rd32(IGC_RCTL);
-	wr32(IGC_RCTL, rctl & ~IGC_RCTL_EN);
-	/* flush and sleep below */
-
+	if (pci_device_is_present(adapter->pdev)) {
+		/* disable receives in the hardware */
+		rctl = rd32(IGC_RCTL);
+		wr32(IGC_RCTL, rctl & ~IGC_RCTL_EN);
+		/* flush and sleep below */
+	}
 	/* set trans_start so we don't get spurious watchdogs during reset */
 	netif_trans_update(netdev);
 
 	netif_carrier_off(netdev);
 	netif_tx_stop_all_queues(netdev);
 
-	/* disable transmits in the hardware */
-	tctl = rd32(IGC_TCTL);
-	tctl &= ~IGC_TCTL_EN;
-	wr32(IGC_TCTL, tctl);
-	/* flush both disables and wait for them to finish */
-	wrfl();
-	usleep_range(10000, 20000);
+	if (pci_device_is_present(adapter->pdev)) {
+		/* disable transmits in the hardware */
+		tctl = rd32(IGC_TCTL);
+		tctl &= ~IGC_TCTL_EN;
+		wr32(IGC_TCTL, tctl);
+		/* flush both disables and wait for them to finish */
+		wrfl();
+		usleep_range(10000, 20000);
 
-	igc_irq_disable(adapter);
+		igc_irq_disable(adapter);
+	}
 
 	adapter->flags &= ~IGC_FLAG_NEED_LINK_UPDATE;
 

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

@@ -849,7 +849,8 @@ void igc_ptp_suspend(struct igc_adapter *adapter)
 	adapter->ptp_tx_skb = NULL;
 	clear_bit_unlock(__IGC_PTP_TX_IN_PROGRESS, &adapter->state);
 
-	igc_ptp_time_save(adapter);
+	if (pci_device_is_present(adapter->pdev))
+		igc_ptp_time_save(adapter);
 }
 
 /**