[pulseaudio-discuss] Soundcard's powersave mode

[Mikhail Morfikov]

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W dniu 2015-10-05 o 01:27, Tanu Kaskinen pisze:
> On Sun, 2015-10-04 at 20:28 +0200, Mikhail Morfikov wrote:
>> In the case of snd_hda_intel kernel module, there's two options called
>> power_save and power_save_controller . I've set them to the following
>> values:
>>
>> # systool -v -m snd_hda_intel | grep power
>>     power_save          = "10"
>>     power_save_controller= "Y"
>>     
>> According to archlinux wiki (https://wiki.archlinux.org/index.php/Power_management#Audio),
>> the power_save parameter is measured in seconds, and it should idle the
>> audio card after 10s.
>>
>> The question is how could I know whether this works or not? Is there
>> any way to be sure that the powersave mode was activated? I've heard
>> that there's could be some "clicking" when the state of the sound
>> card changes, but I don't hear anything. Some people reported that the
>> volume behaves really strange, but it seems that it works just fine on
>> my machine.
>>
>> Does the powersave mode in the kernel module is somehow related to the
>> following output?
>>
>> $ pacmd list-sinks | egrep -i "state|suspend"
>>         state: SUSPENDED
>>         suspend cause: IDLE
>>
>> I noticed that when some app plays audio stream, the state becomes
>> RUNNING. When the app stops playing, the state changes to IDLE, and
>> about 5s later, it changes to the state that you can see above. This
>> behavior is the same no matter what I set in the power_save option
>> in the kernel module. I've tested 0, 1 and 10, and actually I didn't
>> notice any difference.
>>
>> So, is the powersave mode enabled or not?
> 
> I'm not familiar with the kenel module, so I can't answer most of your
> questions. However, I can tell you that the PulseAudio sink state (IDLE
> or SUSPENDED) is not the same thing as the kernel driver's power save
> state. Based on your description, the driver enters the power save mode
> 10 seconds after the PulseAudio sink state has changed to SUSPENDED
> (suspending means that PulseAudio closes the alsa device).
> 

So it should work. Though I have no idea how to check the state of the
soundcard.
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