sound/designs/powersave.rst

2 Notes on Power-Saving Mode
5 AC97 and HD-audio drivers have the automatic power-saving mode.
9 With the automatic power-saving, the driver turns off the codec power
11 the device and/or no analog loopback is set, the power disablement is
15 The time-out for automatic power-off can be specified via ``power_save``
16 module option of snd-ac97-codec and snd-hda-intel modules.  Specify
17 the time-out value in seconds.  0 means to disable the automatic
18 power-saving.  The default value of timeout is given via
21 (the minimum value) isn't recommended because many applications try to
22 reopen the device frequently.  10 would be a good choice for normal
25 The ``power_save`` option is exported as writable.  This means you can
26 adjust the value via sysfs on the fly.  For example, to turn on the
27 automatic power-save mode with 10 seconds, write to
34 Note that you might hear click noise/pop when changing the power
35 state.  Also, it often takes certain time to wake up from the
36 power-down to the active state.  These are often hardly to fix, so
37 don't report extra bug reports unless you have a fix patch ;-)
39 For HD-audio interface, there is another module option,
40 power_save_controller.  This enables/disables the power-save mode of
41 the controller side.  Setting this on may reduce a bit more power
42 consumption, but might result in longer wake-up time and click noise.