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

[Takashi Iwai <tiwai@suse.de>]

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@ffwll.ch; alsa-devel@alsa-project.org;
> > intel-gfx@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-power
> > > 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.  The former is unknown, but better to check pm-utils
hooks and udev rules.


Takashi