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

[Wang xingchao]

On Sat, Jul 06, 2013 at 08:20:59AM +0200, Takashi Iwai wrote:
> > >> >> > drm-intel-next. I'll show up in the next linux-next and I'll forward it to
> > >> >> > Dave for mergin into drm-next in roughly 2 weeks.
> > >> >>
> > >> >> So today I unblacklisted the audio modules on one of my Haswell
> > >> >> machines and booted it with i915.disable_power_well=1. I only have an
> > >> >> eDP output (it doesn't have audio) and I see the power well is
> > >> >> enabled. This is wrong, the power well should be disabled since we
> > >> >
> > >> > right, if no application using audio it should be in runtime suspend mode.
> > >> > And maybe your system didnot enable runtime suspend by default, would you
> > >> > tell me the output below?
> > >> > cat /sys/devices/pci0000:00/0000:00:03.0/power/control
> > >>
> > >> It says "on".
> > >
> > > would you change it to "auto" and test again.
> > > Runtime power save should be enabled with "auto".
> > 
> > Doesn't solve the problem. Should I open a bug report somewhere?
> > Having the power well enabled prevents some power saving features from
> > the graphics driver.
> 
> Is the HD-audio power-saving itself working?  You can check it via
> watching /sys/class/hwC*/power_{on|off}_acct files.

I have two Haswell boards, one with "auto" power-save setting, the other one
has setting "on". Here's the power_on/off_acct values:
1) with control setting "auto"
power_on_acct 14328
power_off_acct 3231848
2) with control setting "on"
power_on_acct 6330528 
power_off_acct 0

So for the second one, power is always on.

Paulo, would you check with your BIOS version? 
At least i found BIOS 131 has the default setting "on" while BIOS 128 has
"auto" setting.

thanks
--xingchao
> 
> power_save option has to be adjusted appropriately.  Note that many
> DEs change this value dynamically per AC-cable plug/unplug depending
> on the configuration, and often it's set to 0 (= no power save) when
> AC-cable is plugged.
> 
>