[alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API implementation for Haswell

[Wang, Xingchao]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Wednesday, July 24, 2013 9:43 PM
> To: Wang, Xingchao
> Cc: Wysocki, Rafael J; David Henningsson; Paulo Zanoni; Daniel Vetter;
> daniel.vetter at ffwll.ch; alsa-devel at alsa-project.org;
> intel-gfx at lists.freedesktop.org; Girdwood, Liam R; Jin, Gordon
> Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API
> implementation for Haswell
> 
> At Wed, 24 Jul 2013 13:30:16 +0000,
> Wang, Xingchao wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Wysocki, Rafael J
> > > Sent: Wednesday, July 24, 2013 9:15 PM
> > > To: David Henningsson
> > > Cc: Wang, Xingchao; Takashi Iwai; Paulo Zanoni; Daniel Vetter;
> > > daniel.vetter at ffwll.ch; alsa-devel at alsa-project.org;
> > > intel-gfx at lists.freedesktop.org; Girdwood, Liam R; Jin, Gordon
> > > Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API
> > > implementation for Haswell
> > >
> > > On 7/24/2013 1:57 PM, David Henningsson wrote:
> > > > On 07/24/2013 01:33 PM, Wang, Xingchao wrote:
> > > >> Yes, I agree. I'm debugging this issue on Ubuntu, not sure it
> > > >> happens on other distribution too.
> > > >> If it's related to Ubuntu, maybe need check Ubuntu power policy.
> > > >> Does anyone know the Ubuntu power-policy on laptop?
> > > >> i.e. when charger connected, will Ubuntu make decision to disable
> > > >> power-save feature for audio subsystem?
> > > >
> > > > I'm not a power management expert, but I got a pointer from my
> > > > team mate to pm-utils:
> > > >
> > > > http://cgit.freedesktop.org/pm-utils/tree/pm/power.d/intel-audio-p
> > > > ower
> > > > save
> > > >
> > > >
> > > > If I understand correctly, The scripts in power.d are executed
> > > > when battery / AC-power is changed.
> > > >
> > >
> > > To me, this sounds like a user space issue.  It requested power on
> > > and the kernel delivered.
> >
> > Do you know which user-space application will touch below two flags?
> > - /sys/devices/pci0000\:00/0000\:00\:03.0/power/control
> > - /sys/module/snd_hda_intel/parameters/power_save
> 
> The latter is touched most likely by pm-utils, one of the hooks, as David pointed.

Oh yes I found the hook:
./pm/power.d/intel-audio-powersave

--xingchao
> The former is unknown, but better to check pm-utils hooks and udev rules.
> 
> 
> Takashi