[ALSA] hda-intel - Add POWER_SAVE option

Added CONFIG_SND_HDA_POWER_SAVE kconfig.  It's an experimental option
to achieve an aggressive power-saving.  With this option, the driver
will turn on/off the power of each codec and controller chip dynamically
on demand.
The patch introduces a new module option 'power_save'.  It specifies
the second of time-out for automatic power-down.  As default, it's
10 seconds.  Setting 0 means to suppress the power-saving feature.
The codec may have analog-input loopbacks, which are usually represented
by mixer elements such as 'Mic Playback Switch' or 'CD Playback Switch'.
When these are on, we cannot turn off the mixer and the codec chip has
to be kept on.  For bookkeeping these states, a new codec-callback is
introduced.
For the bus-controller side, a new callback pm_notify is introduced,
which can be used to turn on/off the contoller appropriately.
Note that this power-saving might cause slight click-noise at
power-on/off.  Also, it might take some time to wake up the codec, and
might even drop some tones at the very beginning.  This seems to be the
side-effect of turning off the controller chip.
This turn-off of the controller can be disabled by undefining
HDA_POWER_SAVE_RESET_CONTOLLER in hda_intel.c.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 8 insertions, 0 deletions

diff --git a/sound/pci/Kconfig b/sound/pci/Kconfig
index ff7a689c229e..9554140f0b04 100644
--- a/sound/pci/Kconfig
+++ b/sound/pci/Kconfig
@@ -581,6 +581,14 @@ config SND_HDA_GENERIC
           Say Y here to enable the generic HD-audio codec parser
           in snd-hda-intel driver.
 
+config SND_HDA_POWER_SAVE
+        bool "Aggressive power-saving on HD-audio"
+        depends on SND_HDA_INTEL && EXPERIMENTAL
+        help
+          Say Y here to enable more aggressive power-saving mode on
+          HD-audio driver.  The power-saving timeout can be configured
+          via power_save option or over sysfs on-the-fly.
+
 config SND_HDSP
         tristate "RME Hammerfall DSP Audio"
         depends on SND