igb: Add mechanism for detecting latched hardware Rx timestamp

Add a check against possible Rx timestamp freezing in the hardware via
watchdog mechanism. This situation can occur when an Rx timestamp has been
latched, but the packet has been dropped because the Rx ring is full.

Whenever a packet comes in that should be timestamped, the Rx timestamp
gets latched into the hardware registers and we will store the jiffy value
in the rx_ring. The watchdog will keep track of his own jiffy timer
whenever there is no valid timestamp in the registers.

If the watchdog detects a valid timestamp in the registers, meaning that no
Rx packet has consumed it yet, it will check which time is most recent: the
last time in the watchdog or any time in the rx_rings. If the most recent
"event" was more than 5 seconds ago, it will flush the Rx timestamp and
print a warning message to the syslog.

Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jacob Keller <Jacob.e.keller@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index 086af4683544..2ec53d7ca1b7 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -429,6 +429,51 @@ static void igb_ptp_overflow_check(struct work_struct *work)
 }
 
 /**
+ * igb_ptp_rx_hang - detect error case when Rx timestamp registers latched
+ * @adapter: private network adapter structure
+ *
+ * This watchdog task is scheduled to detect error case where hardware has
+ * dropped an Rx packet that was timestamped when the ring is full. The
+ * particular error is rare but leaves the device in a state unable to timestamp
+ * any future packets.
+ */
+void igb_ptp_rx_hang(struct igb_adapter *adapter)
+{
+	struct e1000_hw *hw = &adapter->hw;
+	struct igb_ring *rx_ring;
+	u32 tsyncrxctl = rd32(E1000_TSYNCRXCTL);
+	unsigned long rx_event;
+	int n;
+
+	if (hw->mac.type != e1000_82576)
+		return;
+
+	/* If we don't have a valid timestamp in the registers, just update the
+	 * timeout counter and exit
+	 */
+	if (!(tsyncrxctl & E1000_TSYNCRXCTL_VALID)) {
+		adapter->last_rx_ptp_check = jiffies;
+		return;
+	}
+
+	/* Determine the most recent watchdog or rx_timestamp event */
+	rx_event = adapter->last_rx_ptp_check;
+	for (n = 0; n < adapter->num_rx_queues; n++) {
+		rx_ring = adapter->rx_ring[n];
+		if (time_after(rx_ring->last_rx_timestamp, rx_event))
+			rx_event = rx_ring->last_rx_timestamp;
+	}
+
+	/* Only need to read the high RXSTMP register to clear the lock */
+	if (time_is_before_jiffies(rx_event + 5 * HZ)) {
+		rd32(E1000_RXSTMPH);
+		adapter->last_rx_ptp_check = jiffies;
+		adapter->rx_hwtstamp_cleared++;
+		dev_warn(&adapter->pdev->dev, "clearing Rx timestamp hang");
+	}
+}
+
+/**
  * igb_ptp_tx_hwtstamp - utility function which checks for TX time stamp
  * @adapter: Board private structure.
  *