net/mlx5e: Revert parameters on errors when changing PTP state without reset

Port timestamping for PTP can be enabled/disabled while the channels are
closed. In that case mlx5e_safe_switch_channels is skipped, and the
preactivate hook is called directly. However, if that hook returns an
error, the channel parameters must be reverted back to their old values.
This commit adds missing handling on this case.

Fixes: 145e5637 ("net/mlx5e: Add TX PTP port object support")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -2014,8 +2014,13 @@ static int set_pflag_tx_port_ts(struct net_device *netdev, bool enable)
 	 */
 
 	if (!test_bit(MLX5E_STATE_OPENED, &priv->state)) {
+		struct mlx5e_params old_params;
+
+		old_params = priv->channels.params;
 		priv->channels.params = new_channels.params;
 		err = mlx5e_num_channels_changed(priv);
+		if (err)
+			priv->channels.params = old_params;
 		goto out;
 	}