ixgbe: Inline Rx PTP descriptor handling

This change is meant to inline the Rx PTP descriptor handling.  The main
motivation is to avoid unnecessary jumps into function calls that we then
immediately exit because we are not performing timestamps.

The net result of this change is that ixgbe_ptp_rx_tstamp drops from .5% CPU
utilization in my performance runs to 0%, and the only value tested is the Rx
descriptor which should already be warm in the cache if not stored in a
register.

Cc: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Jacob Keller <Jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe.h

@@ -755,9 +755,24 @@ extern void ixgbe_ptp_init(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_stop(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_overflow_check(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_rx_hang(struct ixgbe_adapter *adapter);
-extern void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
-				  union ixgbe_adv_rx_desc *rx_desc,
-				  struct sk_buff *skb);
+extern void __ixgbe_ptp_rx_hwtstamp(struct ixgbe_q_vector *q_vector,
+				    struct sk_buff *skb);
+static inline void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
+					 union ixgbe_adv_rx_desc *rx_desc,
+					 struct sk_buff *skb)
+{
+	if (unlikely(!ixgbe_test_staterr(rx_desc, IXGBE_RXDADV_STAT_TS)))
+		return;
+
+	__ixgbe_ptp_rx_hwtstamp(rx_ring->q_vector, skb);
+
+	/*
+	 * Update the last_rx_timestamp timer in order to enable watchdog check
+	 * for error case of latched timestamp on a dropped packet.
+	 */
+	rx_ring->last_rx_timestamp = jiffies;
+}
+
 extern int ixgbe_ptp_hwtstamp_ioctl(struct ixgbe_adapter *adapter,
 				    struct ifreq *ifr, int cmd);
 extern void ixgbe_ptp_start_cyclecounter(struct ixgbe_adapter *adapter);

drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c

@@ -531,18 +531,16 @@ static void ixgbe_ptp_tx_hwtstamp_work(struct work_struct *work)
 }
 
 /**
- * ixgbe_ptp_rx_hwtstamp - utility function which checks for RX time stamp
+ * __ixgbe_ptp_rx_hwtstamp - utility function which checks for RX time stamp
  * @q_vector: structure containing interrupt and ring information
- * @rx_desc: the rx descriptor
  * @skb: particular skb to send timestamp with
  *
  * if the timestamp is valid, we convert it into the timecounter ns
  * value, then store that result into the shhwtstamps structure which
  * is passed up the network stack
  */
-void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
-			   union ixgbe_adv_rx_desc *rx_desc,
-			   struct sk_buff *skb)
+void __ixgbe_ptp_rx_hwtstamp(struct ixgbe_q_vector *q_vector,
+			     struct sk_buff *skb)
 {
 	struct ixgbe_adapter *adapter;
 	struct ixgbe_hw *hw;
@@ -552,15 +550,12 @@ void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
 	unsigned long flags;
 
 	/* we cannot process timestamps on a ring without a q_vector */
-	if (!rx_ring->q_vector || !rx_ring->q_vector->adapter)
+	if (!q_vector || !q_vector->adapter)
 		return;
 
-	adapter = rx_ring->q_vector->adapter;
+	adapter = q_vector->adapter;
 	hw = &adapter->hw;
 
-	if (unlikely(!ixgbe_test_staterr(rx_desc, IXGBE_RXDADV_STAT_TS)))
-		return;
-
 	/*
 	 * Read the tsyncrxctl register afterwards in order to prevent taking an
 	 * I/O hit on every packet.
@@ -569,12 +564,6 @@ void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
 	if (!(tsyncrxctl & IXGBE_TSYNCRXCTL_VALID))
 		return;
 
-	/*
-	 * Update the last_rx_timestamp timer in order to enable watchdog check
-	 * for error case of latched timestamp on a dropped packet.
-	 */
-	rx_ring->last_rx_timestamp = jiffies;
-
 	regval |= (u64)IXGBE_READ_REG(hw, IXGBE_RXSTMPL);
 	regval |= (u64)IXGBE_READ_REG(hw, IXGBE_RXSTMPH) << 32;