i40e/i40evf: refactor tx timeout logic

This patch modifies the driver timeout logic by issuing a writeback
request via a software interrupt to the hardware the first time the
driver detects a hang. The driver was too aggressive in resetting a hung
queue, so back that off by removing logic to down the netdevice after
too many hangs, and move the function to the service task.

Change-ID: Ife100b9d124cd08cbdb81ab659008c1b9abbedea
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e.h

@@ -243,7 +243,6 @@ struct i40e_pf {
 	struct pci_dev *pdev;
 	struct i40e_hw hw;
 	unsigned long state;
-	unsigned long link_check_timeout;
 	struct msix_entry *msix_entries;
 	bool fc_autoneg_status;
 

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -600,7 +600,6 @@ void i40e_free_tx_resources(struct i40e_ring *tx_ring)
 	}
 }
 
-
 /**
  * i40e_get_tx_pending - how many tx descriptors not processed
  * @tx_ring: the ring of descriptors
@@ -608,7 +607,7 @@ void i40e_free_tx_resources(struct i40e_ring *tx_ring)
  * Since there is no access to the ring head register
  * in XL710, we need to use our local copies
  **/
-static u32 i40e_get_tx_pending(struct i40e_ring *ring)
+u32 i40e_get_tx_pending(struct i40e_ring *ring)
 {
 	u32 head, tail;
 
@@ -622,50 +621,6 @@ static u32 i40e_get_tx_pending(struct i40e_ring *ring)
 	return 0;
 }
 
-/**
- * i40e_check_tx_hang - Is there a hang in the Tx queue
- * @tx_ring: the ring of descriptors
- **/
-static bool i40e_check_tx_hang(struct i40e_ring *tx_ring)
-{
-	u32 tx_done = tx_ring->stats.packets;
-	u32 tx_done_old = tx_ring->tx_stats.tx_done_old;
-	u32 tx_pending = i40e_get_tx_pending(tx_ring);
-	struct i40e_pf *pf = tx_ring->vsi->back;
-	bool ret = false;
-
-	clear_check_for_tx_hang(tx_ring);
-
-	/* Check for a hung queue, but be thorough. This verifies
-	 * that a transmit has been completed since the previous
-	 * check AND there is at least one packet pending. The
-	 * ARMED bit is set to indicate a potential hang. The
-	 * bit is cleared if a pause frame is received to remove
-	 * false hang detection due to PFC or 802.3x frames. By
-	 * requiring this to fail twice we avoid races with
-	 * PFC clearing the ARMED bit and conditions where we
-	 * run the check_tx_hang logic with a transmit completion
-	 * pending but without time to complete it yet.
-	 */
-	if ((tx_done_old == tx_done) && tx_pending) {
-		/* make sure it is true for two checks in a row */
-		ret = test_and_set_bit(__I40E_HANG_CHECK_ARMED,
-				       &tx_ring->state);
-	} else if (tx_done_old == tx_done &&
-		   (tx_pending < I40E_MIN_DESC_PENDING) && (tx_pending > 0)) {
-		if (I40E_DEBUG_FLOW & pf->hw.debug_mask)
-			dev_info(tx_ring->dev, "HW needs some more descs to do a cacheline flush. tx_pending %d, queue %d",
-				 tx_pending, tx_ring->queue_index);
-		pf->tx_sluggish_count++;
-	} else {
-		/* update completed stats and disarm the hang check */
-		tx_ring->tx_stats.tx_done_old = tx_done;
-		clear_bit(__I40E_HANG_CHECK_ARMED, &tx_ring->state);
-	}
-
-	return ret;
-}
-
 #define WB_STRIDE 0x3
 
 /**
@@ -783,32 +738,6 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
 	else
 		tx_ring->arm_wb = false;
 
-	if (check_for_tx_hang(tx_ring) && i40e_check_tx_hang(tx_ring)) {
-		/* schedule immediate reset if we believe we hung */
-		dev_info(tx_ring->dev, "Detected Tx Unit Hang\n"
-			 "  VSI                  <%d>\n"
-			 "  Tx Queue             <%d>\n"
-			 "  next_to_use          <%x>\n"
-			 "  next_to_clean        <%x>\n",
-			 tx_ring->vsi->seid,
-			 tx_ring->queue_index,
-			 tx_ring->next_to_use, i);
-
-		netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
-
-		dev_info(tx_ring->dev,
-			 "tx hang detected on queue %d, reset requested\n",
-			 tx_ring->queue_index);
-
-		/* do not fire the reset immediately, wait for the stack to
-		 * decide we are truly stuck, also prevents every queue from
-		 * simultaneously requesting a reset
-		 */
-
-		/* the adapter is about to reset, no point in enabling polling */
-		budget = 1;
-	}
-
 	netdev_tx_completed_queue(netdev_get_tx_queue(tx_ring->netdev,
 						      tx_ring->queue_index),
 				  total_packets, total_bytes);
@@ -838,7 +767,7 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
  * @q_vector: the vector  on which to force writeback
  *
  **/
-static void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector)
+void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector)
 {
 	u16 flags = q_vector->tx.ring[0].flags;
 

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -199,8 +199,6 @@ struct i40e_rx_queue_stats {
 enum i40e_ring_state_t {
 	__I40E_TX_FDIR_INIT_DONE,
 	__I40E_TX_XPS_INIT_DONE,
-	__I40E_TX_DETECT_HANG,
-	__I40E_HANG_CHECK_ARMED,
 	__I40E_RX_PS_ENABLED,
 	__I40E_RX_16BYTE_DESC_ENABLED,
 };
@@ -211,12 +209,6 @@ enum i40e_ring_state_t {
 	set_bit(__I40E_RX_PS_ENABLED, &(ring)->state)
 #define clear_ring_ps_enabled(ring) \
 	clear_bit(__I40E_RX_PS_ENABLED, &(ring)->state)
-#define check_for_tx_hang(ring) \
-	test_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
-#define set_check_for_tx_hang(ring) \
-	set_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
-#define clear_check_for_tx_hang(ring) \
-	clear_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
 #define ring_is_16byte_desc_enabled(ring) \
 	test_bit(__I40E_RX_16BYTE_DESC_ENABLED, &(ring)->state)
 #define set_ring_16byte_desc_enabled(ring) \
@@ -326,6 +318,8 @@ int i40e_xmit_descriptor_count(struct sk_buff *skb, struct i40e_ring *tx_ring);
 int i40e_tx_prepare_vlan_flags(struct sk_buff *skb,
 			       struct i40e_ring *tx_ring, u32 *flags);
 #endif
+void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector);
+u32 i40e_get_tx_pending(struct i40e_ring *ring);
 
 /**
  * i40e_get_head - Retrieve head from head writeback

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -140,65 +140,6 @@ static inline u32 i40e_get_head(struct i40e_ring *tx_ring)
 	return le32_to_cpu(*(volatile __le32 *)head);
 }
 
-/**
- * i40e_get_tx_pending - how many tx descriptors not processed
- * @tx_ring: the ring of descriptors
- *
- * Since there is no access to the ring head register
- * in XL710, we need to use our local copies
- **/
-static u32 i40e_get_tx_pending(struct i40e_ring *ring)
-{
-	u32 head, tail;
-
-	head = i40e_get_head(ring);
-	tail = readl(ring->tail);
-
-	if (head != tail)
-		return (head < tail) ?
-			tail - head : (tail + ring->count - head);
-
-	return 0;
-}
-
-/**
- * i40e_check_tx_hang - Is there a hang in the Tx queue
- * @tx_ring: the ring of descriptors
- **/
-static bool i40e_check_tx_hang(struct i40e_ring *tx_ring)
-{
-	u32 tx_done = tx_ring->stats.packets;
-	u32 tx_done_old = tx_ring->tx_stats.tx_done_old;
-	u32 tx_pending = i40e_get_tx_pending(tx_ring);
-	bool ret = false;
-
-	clear_check_for_tx_hang(tx_ring);
-
-	/* Check for a hung queue, but be thorough. This verifies
-	 * that a transmit has been completed since the previous
-	 * check AND there is at least one packet pending. The
-	 * ARMED bit is set to indicate a potential hang. The
-	 * bit is cleared if a pause frame is received to remove
-	 * false hang detection due to PFC or 802.3x frames. By
-	 * requiring this to fail twice we avoid races with
-	 * PFC clearing the ARMED bit and conditions where we
-	 * run the check_tx_hang logic with a transmit completion
-	 * pending but without time to complete it yet.
-	 */
-	if ((tx_done_old == tx_done) && tx_pending) {
-		/* make sure it is true for two checks in a row */
-		ret = test_and_set_bit(__I40E_HANG_CHECK_ARMED,
-				       &tx_ring->state);
-	} else if (tx_done_old == tx_done &&
-		   (tx_pending < I40E_MIN_DESC_PENDING) && (tx_pending > 0)) {
-		/* update completed stats and disarm the hang check */
-		tx_ring->tx_stats.tx_done_old = tx_done;
-		clear_bit(__I40E_HANG_CHECK_ARMED, &tx_ring->state);
-	}
-
-	return ret;
-}
-
 #define WB_STRIDE 0x3
 
 /**
@@ -304,6 +245,10 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
 	tx_ring->q_vector->tx.total_bytes += total_bytes;
 	tx_ring->q_vector->tx.total_packets += total_packets;
 
+	/* check to see if there are any non-cache aligned descriptors
+	 * waiting to be written back, and kick the hardware to force
+	 * them to be written back in case of napi polling
+	 */
 	if (budget &&
 	    !((i & WB_STRIDE) == WB_STRIDE) &&
 	    !test_bit(__I40E_DOWN, &tx_ring->vsi->state) &&
@@ -312,29 +257,6 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
 	else
 		tx_ring->arm_wb = false;
 
-	if (check_for_tx_hang(tx_ring) && i40e_check_tx_hang(tx_ring)) {
-		/* schedule immediate reset if we believe we hung */
-		dev_info(tx_ring->dev, "Detected Tx Unit Hang\n"
-			 "  VSI                  <%d>\n"
-			 "  Tx Queue             <%d>\n"
-			 "  next_to_use          <%x>\n"
-			 "  next_to_clean        <%x>\n",
-			 tx_ring->vsi->seid,
-			 tx_ring->queue_index,
-			 tx_ring->next_to_use, i);
-
-		netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
-
-		dev_info(tx_ring->dev,
-			 "tx hang detected on queue %d, resetting adapter\n",
-			 tx_ring->queue_index);
-
-		tx_ring->netdev->netdev_ops->ndo_tx_timeout(tx_ring->netdev);
-
-		/* the adapter is about to reset, no point in enabling stuff */
-		return true;
-	}
-
 	netdev_tx_completed_queue(netdev_get_tx_queue(tx_ring->netdev,
 						      tx_ring->queue_index),
 				  total_packets, total_bytes);
@@ -355,16 +277,16 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
 		}
 	}
 
-	return budget > 0;
+	return !!budget;
 }
 
 /**
- * i40e_force_wb -Arm hardware to do a wb on noncache aligned descriptors
+ * i40evf_force_wb -Arm hardware to do a wb on noncache aligned descriptors
  * @vsi: the VSI we care about
  * @q_vector: the vector  on which to force writeback
  *
  **/
-static void i40e_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector)
+static void i40evf_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector)
 {
 	u16 flags = q_vector->tx.ring[0].flags;
 
@@ -1385,7 +1307,7 @@ int i40evf_napi_poll(struct napi_struct *napi, int budget)
 	/* If work not completed, return budget and polling will return */
 	if (!clean_complete) {
 		if (arm_wb)
-			i40e_force_wb(vsi, q_vector);
+			i40evf_force_wb(vsi, q_vector);
 		return budget;
 	}
 

drivers/net/ethernet/intel/i40evf/i40e_txrx.h

@@ -198,8 +198,6 @@ struct i40e_rx_queue_stats {
 enum i40e_ring_state_t {
 	__I40E_TX_FDIR_INIT_DONE,
 	__I40E_TX_XPS_INIT_DONE,
-	__I40E_TX_DETECT_HANG,
-	__I40E_HANG_CHECK_ARMED,
 	__I40E_RX_PS_ENABLED,
 	__I40E_RX_16BYTE_DESC_ENABLED,
 };
@@ -210,12 +208,6 @@ enum i40e_ring_state_t {
 	set_bit(__I40E_RX_PS_ENABLED, &(ring)->state)
 #define clear_ring_ps_enabled(ring) \
 	clear_bit(__I40E_RX_PS_ENABLED, &(ring)->state)
-#define check_for_tx_hang(ring) \
-	test_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
-#define set_check_for_tx_hang(ring) \
-	set_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
-#define clear_check_for_tx_hang(ring) \
-	clear_bit(__I40E_TX_DETECT_HANG, &(ring)->state)
 #define ring_is_16byte_desc_enabled(ring) \
 	test_bit(__I40E_RX_16BYTE_DESC_ENABLED, &(ring)->state)
 #define set_ring_16byte_desc_enabled(ring) \