1 ==========================
2 Notes on Power-Saving Mode
3 ==========================
4
5 AC97 and HD-audio drivers have the automatic p
6 This feature is enabled via Kconfig ``CONFIG_S
7 and ``CONFIG_SND_HDA_POWER_SAVE`` options, res
8
9 With the automatic power-saving, the driver tu
10 appropriately when no operation is required.
11 the device and/or no analog loopback is set, t
12 done fully or partially. It'll save a certain
13 good for laptops (even for desktops).
14
15 The time-out for automatic power-off can be sp
16 module option of snd-ac97-codec and snd-hda-in
17 the time-out value in seconds. 0 means to dis
18 power-saving. The default value of timeout is
19 ``CONFIG_SND_AC97_POWER_SAVE_DEFAULT`` and
20 ``CONFIG_SND_HDA_POWER_SAVE_DEFAULT`` Kconfig
21 (the minimum value) isn't recommended because
22 reopen the device frequently. 10 would be a g
23 operations.
24
25 The ``power_save`` option is exported as writa
26 adjust the value via sysfs on the fly. For ex
27 automatic power-save mode with 10 seconds, wri
28 ``/sys/modules/snd_ac97_codec/parameters/power
29 ::
30
31 # echo 10 > /sys/modules/snd_ac97_code
32
33
34 Note that you might hear click noise/pop when
35 state. Also, it often takes certain time to w
36 power-down to the active state. These are oft
37 don't report extra bug reports unless you have
38
39 For HD-audio interface, there is another modul
40 power_save_controller. This enables/disables
41 the controller side. Setting this on may redu
42 consumption, but might result in longer wake-u
43 Try to turn it off when you experience such a
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