IB/mlx4: Don't return an invalid speed when a port is down

When the IB port is down, the active_speed value returned by the
MAD_IFC command is seven (7) which isn't among the defined IB speeds
in enum ib_port_speed, and this invalid speed value is passed up to
higher layers or applications who do port query.

Fix that by setting the speed to be SDR -- the lowest possible -- when
the port is down.
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/main.c

@@ -253,6 +253,11 @@ static int ib_link_query_port(struct ib_device *ibdev, u8 port,
 		if (out_mad->data[15] & 0x1)
 			props->active_speed = IB_SPEED_FDR10;
 	}
+
+	/* Avoid wrong speed value returned by FW if the IB link is down. */
+	if (props->state == IB_PORT_DOWN)
+		 props->active_speed = IB_SPEED_SDR;
+
 out:
 	kfree(in_mad);
 	kfree(out_mad);