[Techteam] XO-1.5 Kernel Update (i.e My Weekly Status)

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Tue Jul 21 00:03:32 EDT 2009

John Watlington wrote:
> We have often discussed the need for an audio DCON.
> It wouldn't take much -- the amount of memory required
> for a second of playback/record could be included in
> the codec.
> wad

My impression is that the codec does DMA to memory for recording and
playback.  If DMA works during CPU suspend, then it seems like playback
should "just work".  In fact, if the buffer's big enough, the interrupts
issued by the codec should be able to wake the CPU up in time to
refill/empty the buffer without a glitch.

The power domain charts for XO-1 and XO-1.5 don't quite tell me whether
the codec, amplifiers, northbridge, and southbridge are enough powered in
suspend for this to work.  I imagine not, though, so audio playback will
probably have to inhibit suspend in XO-1.5.  I do not think this will be
difficult to implement in software.


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