net/mlx5e: Poll event queue upon TX timeout before performing full ch…

…annels recovery

Up until this patch, on every TX timeout we would try to do channels
recovery.  However, in case of a lost interrupt for an EQ, the channel
associated to it cannot be recovered if reopened as it would never get
another interrupt on sent/received traffic, and eventually ends up with
another TX timeout (Restarting the EQ is not part of channel recovery).

This patch adds a mechanism for explicitly polling EQ in case of a TX
timeout in order to recover from a lost interrupt. If this is not the
case (no pending EQEs), perform a channels full recovery as usual.

Once a lost EQE is recovered, it triggers the NAPI to run and handle all
pending completions. This will free some budget in the bql (via calling
netdev_tx_completed_queue) or by clearing pending TXWQEs and waking up
the queue.  One of the above actions will move the queue to be ready for
transmit again.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -3757,40 +3757,61 @@ static netdev_features_t mlx5e_features_check(struct sk_buff *skb,
 	return features;
 }
 
+static bool mlx5e_tx_timeout_eq_recover(struct net_device *dev,
+					struct mlx5e_txqsq *sq)
+{
+	struct mlx5e_priv *priv = netdev_priv(dev);
+	struct mlx5_core_dev *mdev = priv->mdev;
+	int irqn_not_used, eqn;
+	struct mlx5_eq *eq;
+	u32 eqe_count;
+
+	if (mlx5_vector2eqn(mdev, sq->cq.mcq.vector, &eqn, &irqn_not_used))
+		return false;
+
+	eq = mlx5_eqn2eq(mdev, eqn);
+	if (IS_ERR(eq))
+		return false;
+
+	netdev_err(dev, "EQ 0x%x: Cons = 0x%x, irqn = 0x%x\n",
+		   eqn, eq->cons_index, eq->irqn);
+
+	eqe_count = mlx5_eq_poll_irq_disabled(eq);
+	if (!eqe_count)
+		return false;
+
+	netdev_err(dev, "Recover %d eqes on EQ 0x%x\n", eqe_count, eq->eqn);
+	return true;
+}
+
 static void mlx5e_tx_timeout(struct net_device *dev)
 {
 	struct mlx5e_priv *priv = netdev_priv(dev);
-	bool sched_work = false;
+	bool reopen_channels = false;
 	int i;
 
 	netdev_err(dev, "TX timeout detected\n");
 
 	for (i = 0; i < priv->channels.num * priv->channels.params.num_tc; i++) {
 		struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, i);
 		struct mlx5e_txqsq *sq = priv->txq2sq[i];
-		struct mlx5_core_dev *mdev = priv->mdev;
-		int irqn_not_used, eqn;
-		struct mlx5_eq *eq;
 
 		if (!netif_xmit_stopped(dev_queue))
 			continue;
-		sched_work = true;
-		clear_bit(MLX5E_SQ_STATE_ENABLED, &sq->state);
 		netdev_err(dev, "TX timeout on queue: %d, SQ: 0x%x, CQ: 0x%x, SQ Cons: 0x%x SQ Prod: 0x%x, usecs since last trans: %u\n",
 			   i, sq->sqn, sq->cq.mcq.cqn, sq->cc, sq->pc,
 			   jiffies_to_usecs(jiffies - dev_queue->trans_start));
 
-		if (mlx5_vector2eqn(mdev, sq->cq.mcq.vector, &eqn,
-				    &irqn_not_used))
-			continue;
-
-		eq = mlx5_eqn2eq(mdev, eqn);
-		if (!IS_ERR(eq))
-			netdev_err(dev, "EQ 0x%x: Cons = 0x%x, irqn = 0x%x\n",
-				   eqn, eq->cons_index, eq->irqn);
+		/* If we recover a lost interrupt, most likely TX timeout will
+		 * be resolved, skip reopening channels
+		 */
+		if (!mlx5e_tx_timeout_eq_recover(dev, sq)) {
+			clear_bit(MLX5E_SQ_STATE_ENABLED, &sq->state);
+			reopen_channels = true;
+		}
 	}
 
-	if (sched_work && test_bit(MLX5E_STATE_OPENED, &priv->state))
+	if (reopen_channels && test_bit(MLX5E_STATE_OPENED, &priv->state))
 		schedule_work(&priv->tx_timeout_work);
 }
 

drivers/net/ethernet/mellanox/mlx5/core/eq.c

@@ -530,6 +530,24 @@ static irqreturn_t mlx5_eq_int(int irq, void *eq_ptr)
 	return IRQ_HANDLED;
 }
 
+/* Some architectures don't latch interrupts when they are disabled, so using
+ * mlx5_eq_poll_irq_disabled could end up losing interrupts while trying to
+ * avoid losing them.  It is not recommended to use it, unless this is the last
+ * resort.
+ */
+u32 mlx5_eq_poll_irq_disabled(struct mlx5_eq *eq)
+{
+	u32 count_eqe;
+
+	disable_irq(eq->irqn);
+	count_eqe = eq->cons_index;
+	mlx5_eq_int(eq->irqn, eq);
+	count_eqe = eq->cons_index - count_eqe;
+	enable_irq(eq->irqn);
+
+	return count_eqe;
+}
+
 static void init_eq_buf(struct mlx5_eq *eq)
 {
 	struct mlx5_eqe *eqe;

drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h

@@ -116,6 +116,7 @@ int mlx5_destroy_scheduling_element_cmd(struct mlx5_core_dev *dev, u8 hierarchy,
 int mlx5_wait_for_vf_pages(struct mlx5_core_dev *dev);
 u64 mlx5_read_internal_timer(struct mlx5_core_dev *dev);
 struct mlx5_eq *mlx5_eqn2eq(struct mlx5_core_dev *dev, int eqn);
+u32 mlx5_eq_poll_irq_disabled(struct mlx5_eq *eq);
 void mlx5_cq_tasklet_cb(unsigned long data);
 
 int mlx5_query_pcam_reg(struct mlx5_core_dev *dev, u32 *pcam, u8 feature_group,