net/mlx5e: Allow mlx5e_switch_priv_channels to fail and recover

Currently mlx5e_switch_priv_channels expects that the preactivate hook
doesn't fail, however, it can fail, because it may set hardware
parameters. This commit addresses this issue and provides a way to
recover from failures of the preactivate hook: the old channels are not
closed until the point where nothing can fail anymore, so in case
preactivate fails, the driver can roll back the old channels and
activate them again.

Signed-off-by: Maxim Mikityanskiy <maximmi@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

@@ -2937,33 +2937,45 @@ void mlx5e_deactivate_priv_channels(struct mlx5e_priv *priv)
 	mlx5e_deactivate_channels(&priv->channels);
 }
 
-static void mlx5e_switch_priv_channels(struct mlx5e_priv *priv,
-				       struct mlx5e_channels *new_chs,
-				       mlx5e_fp_preactivate preactivate)
+static int mlx5e_switch_priv_channels(struct mlx5e_priv *priv,
+				      struct mlx5e_channels *new_chs,
+				      mlx5e_fp_preactivate preactivate)
 {
 	struct net_device *netdev = priv->netdev;
+	struct mlx5e_channels old_chs;
 	int carrier_ok;
+	int err = 0;
 
 	carrier_ok = netif_carrier_ok(netdev);
 	netif_carrier_off(netdev);
 
 	mlx5e_deactivate_priv_channels(priv);
-	mlx5e_close_channels(&priv->channels);
 
+	old_chs = priv->channels;
 	priv->channels = *new_chs;
 
 	/* New channels are ready to roll, call the preactivate hook if needed
 	 * to modify HW settings or update kernel parameters.
 	 */
-	if (preactivate)
-		preactivate(priv);
+	if (preactivate) {
+		err = preactivate(priv);
+		if (err) {
+			priv->channels = old_chs;
+			goto out;
+		}
+	}
 
+	mlx5e_close_channels(&old_chs);
 	priv->profile->update_rx(priv);
+
+out:
 	mlx5e_activate_priv_channels(priv);
 
 	/* return carrier back if needed */
 	if (carrier_ok)
 		netif_carrier_on(netdev);
+
+	return err;
 }
 
 int mlx5e_safe_switch_channels(struct mlx5e_priv *priv,
@@ -2976,8 +2988,16 @@ int mlx5e_safe_switch_channels(struct mlx5e_priv *priv,
 	if (err)
 		return err;
 
-	mlx5e_switch_priv_channels(priv, new_chs, preactivate);
+	err = mlx5e_switch_priv_channels(priv, new_chs, preactivate);
+	if (err)
+		goto err_close;
+
 	return 0;
+
+err_close:
+	mlx5e_close_channels(new_chs);
+
+	return err;
 }
 
 int mlx5e_safe_reopen_channels(struct mlx5e_priv *priv)