igc: Check __IGC_PTP_TX_IN_PROGRESS instead of ptp_tx_skb

The __IGC_PTP_TX_IN_PROGRESS flag indicates we have a pending Tx
timestamp. In some places, instead of checking that flag, we check
adapter->ptp_tx_skb. This patch fixes those places to use the flag.

Quick note about igc_ptp_tx_hwtstamp() change: when that function is
called, adapter->ptp_tx_skb is expected to be valid always so we
WARN_ON_ONCE() in case it is not.

Quick note about igc_ptp_suspend() change: when suspending, we don't
really need to check if there is a pending timestamp. We can simply
clear it unconditionally.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

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

@@ -404,9 +404,6 @@ void igc_ptp_tx_hang(struct igc_adapter *adapter)
 	bool timeout = time_is_before_jiffies(adapter->ptp_tx_start +
 					      IGC_PTP_TX_TIMEOUT);
 
-	if (!adapter->ptp_tx_skb)
-		return;
-
 	if (!test_bit(__IGC_PTP_TX_IN_PROGRESS, &adapter->state))
 		return;
 
@@ -435,6 +432,9 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter)
 	struct igc_hw *hw = &adapter->hw;
 	u64 regval;
 
+	if (WARN_ON_ONCE(!skb))
+		return;
+
 	regval = rd32(IGC_TXSTMPL);
 	regval |= (u64)rd32(IGC_TXSTMPH) << 32;
 	igc_ptp_systim_to_hwtstamp(adapter, &shhwtstamps, regval);
@@ -466,7 +466,7 @@ static void igc_ptp_tx_work(struct work_struct *work)
 	struct igc_hw *hw = &adapter->hw;
 	u32 tsynctxctl;
 
-	if (!adapter->ptp_tx_skb)
+	if (!test_bit(__IGC_PTP_TX_IN_PROGRESS, &adapter->state))
 		return;
 
 	if (time_is_before_jiffies(adapter->ptp_tx_start +
@@ -588,11 +588,9 @@ void igc_ptp_suspend(struct igc_adapter *adapter)
 		return;
 
 	cancel_work_sync(&adapter->ptp_tx_work);
-	if (adapter->ptp_tx_skb) {
-		dev_kfree_skb_any(adapter->ptp_tx_skb);
-		adapter->ptp_tx_skb = NULL;
-		clear_bit_unlock(__IGC_PTP_TX_IN_PROGRESS, &adapter->state);
-	}
+	dev_kfree_skb_any(adapter->ptp_tx_skb);
+	adapter->ptp_tx_skb = NULL;
+	clear_bit_unlock(__IGC_PTP_TX_IN_PROGRESS, &adapter->state);
 }
 
 /**