[alsa-devel] [RFC PATCH 5/5] ASoC: omap-mcbsp: Place correct constraints for streams

Jarkko Nikula jhnikula at gmail.com
Tue Jun 1 13:20:47 CEST 2010

On Tue, 1 Jun 2010 13:30:10 +0300
Peter Ujfalusi <peter.ujfalusi at nokia.com> wrote:

> Because, if you want to transfer in one SDMA burst more than the space free in 
> the McBSP FIFO, than where would the rest go?
I would have expected peripheral to deassert the DMA request but I
haven't read the TRM so detail and experimenting with bigger period
sizes didn't work so some /dev/null effect was obviously happening :-)

> I guess it could be better than having 128 word long periods on McBSP1, 3, 4, 
> and 5. With small period size the applications also need to be woken up, but if 
> we silently handling the DMA IRQs, and the application is only woken up by every 
> 10. DMA IRQ, it might still save some power?
This is worth to experiment. Probably more interrupts with or without
application wakeup reduction does not increase power as much as the
savings are from core clocks being more idle.


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