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Name	Size	Permission
ALSA-Configuration.txt.gz	21.98 KB	-rw-r--r--
alsa-parameters.txt	2.07 KB	-rw-r--r--
Audigy-mixer.txt.gz	3.17 KB	-rw-r--r--
Audiophile-Usb.txt.gz	6.21 KB	-rw-r--r--
Bt87x.txt	2.54 KB	-rw-r--r--
CMIPCI.txt.gz	3.87 KB	-rw-r--r--
compress_offload.txt.gz	3.61 KB	-rw-r--r--
ControlNames.txt	2.08 KB	-rw-r--r--
emu10k1-jack.txt	3.24 KB	-rw-r--r--
hda_codec.txt.gz	3.93 KB	-rw-r--r--
HD-Audio-Controls.txt.gz	1.61 KB	-rw-r--r--
HD-Audio-Models.txt.gz	3.1 KB	-rw-r--r--
HD-Audio.txt.gz	11.45 KB	-rw-r--r--
hdspm.txt.gz	3.56 KB	-rw-r--r--
Joystick.txt	3.32 KB	-rw-r--r--
MIXART.txt	3.24 KB	-rw-r--r--
OSS-Emulation.txt.gz	3.91 KB	-rw-r--r--
powersave.txt	1.93 KB	-rw-r--r--
Procfile.txt.gz	2.77 KB	-rw-r--r--
SB-Live-mixer.txt.gz	3.37 KB	-rw-r--r--
seq_oss.html	15.15 KB	-rw-r--r--
serial-u16550.txt	3.99 KB	-rw-r--r--
VIA82xx-mixer.txt	299 B	-rw-r--r--

Code Editor : powersave.txt

Notes on Power-Saving Mode
==========================

AC97 and HD-audio drivers have the automatic power-saving mode.
This feature is enabled via Kconfig CONFIG_SND_AC97_POWER_SAVE
and CONFIG_SND_HDA_POWER_SAVE options, respectively.

With the automatic power-saving, the driver turns off the codec power
appropriately when no operation is required.  When no applications use
the device and/or no analog loopback is set, the power disablement is
done fully or partially.  It'll save a certain power consumption, thus
good for laptops (even for desktops).

The time-out for automatic power-off can be specified via power_save
module option of snd-ac97-codec and snd-hda-intel modules.  Specify
the time-out value in seconds.  0 means to disable the automatic
power-saving.  The default value of timeout is given via
CONFIG_SND_AC97_POWER_SAVE_DEFAULT and
CONFIG_SND_HDA_POWER_SAVE_DEFAULT Kconfig options.  Setting this to 1
(the minimum value) isn't recommended because many applications try to
reopen the device frequently.  10 would be a good choice for normal
operations.

The power_save option is exported as writable.  This means you can
adjust the value via sysfs on the fly.  For example, to turn on the
automatic power-save mode with 10 seconds, write to
/sys/modules/snd_ac97_codec/parameters/power_save (usually as root):

# echo 10 > /sys/modules/snd_ac97_codec/parameters/power_save

Note that you might hear click noise/pop when changing the power
state.  Also, it often takes certain time to wake up from the
power-down to the active state.  These are often hardly to fix, so
don't report extra bug reports unless you have a fix patch ;-)

For HD-audio interface, there is another module option,
power_save_controller.  This enables/disables the power-save mode of
the controller side.  Setting this on may reduce a bit more power
consumption, but might result in longer wake-up time and click noise.
Try to turn it off when you experience such a thing too often.

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Code Editor : powersave.txt