[ALSA] Add experimental support of aggressive AC97 power-saving mode

Added CONFIG_SND_AC97_POWER_SAVE kernel config to enable the support
of aggressive AC97 power-saving mode.  In this mode, the AC97
powerdown register bits are dynamically controlled at each open/close
of PCM streams.
The mode is activated via power_save option for snd-ac97-codec
driver.  As default it's off.  It can be turned on/off on the fly
via sysfs, too.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/sound/drivers/Kconfig b/sound/drivers/Kconfig
index 395c4ef52ac9..897dc2dfd7dd 100644
--- a/sound/drivers/Kconfig
+++ b/sound/drivers/Kconfig
@@ -100,4 +100,17 @@ config SND_MPU401
           To compile this driver as a module, choose M here: the module
           will be called snd-mpu401.
 
+config SND_AC97_POWER_SAVE
+        bool "AC97 Power-Saving Mode"
+        depends on SND_AC97_CODEC && EXPERIMENTAL
+        default n
+        help
+          Say Y here to enable the aggressive power-saving support of
+          AC97 codecs.  In this mode, the power-mode is dynamically
+          controlled at each open/close.
+
+          The mode is activated by passing power_save=1 option to
+          snd-ac97-codec driver.  You can toggle it dynamically over
+          sysfs, too.
+
 endmenu