WARN(num_connectors != 1, "%d connectors attached to pipe %c\n",
             num_connectors, pipe_name(pipe));
 
+       WARN_ON(I915_READ(PIPECONF(pipe)) &
+               (PIPECONF_ENABLE | I965_PIPECONF_ACTIVE));
+
+       WARN_ON(I915_READ(DSPCNTR(plane)) & DISPLAY_PLANE_ENABLE);
+
        if (!intel_ddi_pll_mode_set(crtc, adjusted_mode->clock))
                return -EINVAL;
 
 
        haswell_set_pipeconf(crtc, adjusted_mode, dither);
 
-       intel_wait_for_vblank(dev, pipe);
-
        /* Set up the display plane register */
        I915_WRITE(DSPCNTR(plane), DISPPLANE_GAMMA_ENABLE);
        POSTING_READ(DSPCNTR(plane));