Howdy, When PulseAudio is used and all PCM is routed through PulseAudio (Fedora, Meego, etc), the notion of ALSA periods isn't very useful. PulseAudio uses a timer to refill buffers and the period interrupts are not used at all. So why not disable them entirely to reduce the number of wakeups? This is possible with a number of existing DMA controllers. The simple patch attached shows a proof-of-concept on HDAudio, it's been working for 5 hours on my Fedora12 laptop without any glitches and powertop does show _zero_ wakeups from the HDAudio controller (except on startup). I am told by my colleagues working in Windows environments that this is what's done on Vista/Windows7 btw. This isn't to say Windows is great but that artificial generation of not-needed interrupts is avoidable. There are probably some cases where you don't want this type of behavior (broken hardware, legacy code with multiple-buffering, disabled timer in PulseAudio), so I think it would make sense to request the disabling of interrupts when hw_params are set, since this is also the time when period sizes are set. I am aware that some changes would be needed in pcm_lib.c, where all the error checks are done. Takashi, Jaroslav, Lennart, what do you think? Feedback and suggestions welcome. Cheers - Pierre
Attachment:
0001-hda-remove-HDA-interrupts-when-buffer-is-processed.patch
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