what is about SND_AC97_POWER_SAVE ?

[Alexey Fisher]

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This work around not working for me.

It seems sysfs options for snd_ac97_codec true only for new devices.
It's mean you need reload snd_card_driver to make youse of this changes
 or just
echo "options snd_ac97_codec power_save=1" >> /etc/modprobe.d/options

this working for me well.
i don't think this is a bug, the same is for usb_core/autosuspend this
working only for new devices too. Only difference is that every sysfs
usb_device have this options but not sound_devices.

power_save options is experimental and disabled default, so a leak of
explanation in kernel or on powertop webseite is the problem.

Alexey Fisher


Peter Ganzhorn wrote:
> I got an idea for a possible workaround until this issue is fixed:
> If using the sysfs interface to set the powermanagement of AC97, you
> will most probably set it in an init script, I did in /etc/rc.local .
> After you set the value to "Y" (or "1"), you need to play a sound once
> to trigger the power suspend - so why not add a second line to your init
> script:
> 
> echo "0" > /dev/dsp
> 
> I haven't tested if this really works in the init script, but when I do
> this, I can hear the typical power-resume clicking noise throught my
> speakers. 
> So for the driver a sound was played and hence the device should be
> suspended afterwards when the autosuspend parameter is set.
> If anyone tries this at startup before me let me know if this trick
> works, but I'm confident this should do as a workaround for now.
> 
> Peter Ganzhorn
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