Hi, [resent due to a size limit - now the patch gzipped and attached] the patch below is an experimental patch to achieve more aggressive power-saving on HD-audio. With the patch, the device is disabled after a certain timeout when no apps are using the PCM and no loopback channels are being used. (According to Pavel Machek, sound chips consume significant powers.) For some reasons, the patch is a bit intrusive and touches many places. But the change is pretty straightforward: add power-up/down calls in appropriate place (e.g. mixer changes, PCM open/close). For the power-up/down control, a damn simple way is chosen in this version. The driver does basically a same job like suspend/resume. We can tune up this later if the perfomance matters. The default timeout value is 30 seconds. This is adjustable via power_save module option of snd-hda-intel driver. You can change this value dynamically via writing to /sys/modules/snd_hda_intel/parameters/power_save. The value changed isn't propagated immediately, and you have to do something (like change a mixer value or open/close PCM) to activate the new value, though. Note that my plan is to push this after ALSA 1.0.13-final is released. Thus it's a material for 2.6.20 kernel... yes, we have still a lot of time for debugging. BTW, a similar patch for intel8x0 driver is on my queue. If you're interested in it, let me know. It's still buggy, so I have to debug it first :) Takashi
Attachment:
hda-power-save7.diff.gz
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