net/mlx5: fix link state on device start

Following commit c7bf62255e ("net/mlx5: fix handling link status event")
the link state must be up in order for the burst function to be set on
the device ops.

As the link may take time to move between down and up state it is
possible the rte_eth_dev_start call will return with wrong burst
function (either null or the empty burst function).

Fixing it by forcing the link to be up before returning from device
start. In case the link is still not up after 5 seconds fail the function.
In addition initialize the burst function on device probe to prevent
crashes before the link is up.

Fixes: c7bf62255e ("net/mlx5: fix handling link status event")
Cc: stable@dpdk.org

Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>

drivers/net/mlx5/mlx5.c

@@ -858,6 +858,11 @@ mlx5_pci_probe(struct rte_pci_driver *pci_drv, struct rte_pci_device *pci_dev)
 		eth_dev->device = &pci_dev->device;
 		rte_eth_copy_pci_info(eth_dev, pci_dev);
 		eth_dev->device->driver = &mlx5_driver.driver;
+		/*
+		 * Initialize burst functions to prevent crashes before link-up.
+		 */
+		eth_dev->rx_pkt_burst = removed_rx_burst;
+		eth_dev->tx_pkt_burst = removed_tx_burst;
 		priv->dev = eth_dev;
 		eth_dev->dev_ops = &mlx5_dev_ops;
 		/* Register MAC address. */

drivers/net/mlx5/mlx5.h

@@ -245,6 +245,7 @@ int mlx5_dev_configure(struct rte_eth_dev *);
 void mlx5_dev_infos_get(struct rte_eth_dev *, struct rte_eth_dev_info *);
 const uint32_t *mlx5_dev_supported_ptypes_get(struct rte_eth_dev *dev);
 int priv_link_update(struct priv *, int);
+int priv_force_link_status_change(struct priv *, int);
 int mlx5_link_update(struct rte_eth_dev *, int);
 int mlx5_dev_set_mtu(struct rte_eth_dev *, uint16_t);
 int mlx5_dev_get_flow_ctrl(struct rte_eth_dev *, struct rte_eth_fc_conf *);

drivers/net/mlx5/mlx5_defs.h

@@ -110,4 +110,7 @@
 /* Supported RSS */
 #define MLX5_RSS_HF_MASK (~(ETH_RSS_IP | ETH_RSS_UDP | ETH_RSS_TCP))
 
+/* Maximum number of attempts to query link status before giving up. */
+#define MLX5_MAX_LINK_QUERY_ATTEMPTS 5
+
 #endif /* RTE_PMD_MLX5_DEFS_H_ */

drivers/net/mlx5/mlx5_ethdev.c

@@ -966,6 +966,33 @@ priv_link_update(struct priv *priv, int wait_to_complete)
 	return ret;
 }
 
+/**
+ * Querying the link status till it changes to the desired state.
+ * Number of query attempts is bounded by MLX5_MAX_LINK_QUERY_ATTEMPTS.
+ *
+ * @param priv
+ *   Pointer to private structure.
+ * @param status
+ *   Link desired status.
+ *
+ * @return
+ *   0 on success, negative errno value on failure.
+ */
+int
+priv_force_link_status_change(struct priv *priv, int status)
+{
+	int try = 0;
+
+	while (try < MLX5_MAX_LINK_QUERY_ATTEMPTS) {
+		priv_link_update(priv, 0);
+		if (priv->dev->data->dev_link.link_status == status)
+			return 0;
+		try++;
+		sleep(1);
+	}
+	return -EAGAIN;
+}
+
 /**
  * DPDK callback to retrieve physical link information.
  *

drivers/net/mlx5/mlx5_trigger.c

@@ -166,7 +166,13 @@ mlx5_dev_start(struct rte_eth_dev *dev)
 	priv_xstats_init(priv);
 	/* Update link status and Tx/Rx callbacks for the first time. */
 	memset(&dev->data->dev_link, 0, sizeof(struct rte_eth_link));
-	priv_link_update(priv, 1);
+	INFO("Forcing port %u link to be up", dev->data->port_id);
+	err = priv_force_link_status_change(priv, ETH_LINK_UP);
+	if (err) {
+		DEBUG("Failed to set port %u link to be up",
+		      dev->data->port_id);
+		goto error;
+	}
 	priv_dev_interrupt_handler_install(priv, dev);
 	priv_unlock(priv);
 	return 0;