On 09/02/2016 06:54 PM, Pavel Machek wrote: > Hi! > >>>> When the FIFO is set to 128, it means that after the initial FIFO fill we will >>>> have DMA request coming from McBSP to sDMA with a rate of: >>>> >>>> (1000/sampling_rate) * (FIFO-threshold / channels) = DMA_req_distance_in_ms >>>> >>>> So in case of 44.1KHz, stereo with 128 FIFO threshold DMA request will come at >>>> every 1.45ms. If I'm not mistaken. The whole FIFO (1280) holds 14.51ms of >>>> audio in this case. >>>> >>>> I don't see this correlate with the 30ms at all. >>> >>> It seems we easily have a situation where DMA is done buffering to McBSP, >>> and PMIC is playing audio, and we hit idle. At that point there are no immediate >>> timers pending and cpuidle determines we can try to hit a deeper idle mode. As >>> there are no hardware blockers with DMA off and McBSP not blocking, the hardware >>> hits off mode. This cuts power to McBSP. >>> >>> Ideally we'd configure McBSP activity to block deeper idle states in the >>> hardware but I don't think we have such a configuration available. >> >> I wonder why we have not seen this before? I can not recall anything like this >> with n900 (Jarkko might know that better) neither with n9/n950. On the n9/n950 >> I have even put the OMAP3 to OFF during audio playback with the > > I was seeing something like that with 4.x kernel on Nokia N900. So it must be possible to reproduce it on BeagleBoard-xm... I will try to get the PM working on it and let's see (hear). -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
