GEN8_PIPE_FIFO_UNDERRUN
if (iir & GEN8_PIPE_FIFO_UNDERRUN)
uint32_t extra_ier = GEN8_PIPE_VBLANK | GEN8_PIPE_FIFO_UNDERRUN;
GEN8_PIPE_FIFO_UNDERRUN;
bdw_enable_pipe_irq(dev_priv, pipe, GEN8_PIPE_FIFO_UNDERRUN);
bdw_disable_pipe_irq(dev_priv, pipe, GEN8_PIPE_FIFO_UNDERRUN);