Bug 48381

After updating to kernel 3.6 (from 3.5) I noticed that my laptop speakers seemed to stop working a few minutes after booting. After some investigating I found that the headphone output still works. Also disabling the 'Auto-Mute Mode' with alsamixer makes the laptop's speakers generate sound again.
It seems that after a maybe a minute of inactivity the soundcard goes into a low-power mode (you can hear the speakers 'pop'). Perhaps after this the driver thinks that there is a headphone plugged in while it is not?

As long as there is sound being output the speakers keep working, this only seems to happen after a period of inactivity.



--- Steps to reproduce---
1) Reboot, to ensure that sound works.
2) Test that sound actually works from the built-in speakers, volume is on, nothing is plugged into the headphone jack (mplayer my_favourite_song.wav)
3) Wait a few minutes, with no sound
4) Try to output some sound again (mplayer my_favourite_song.wav)



--- Expected result ---
Sound eminates from the laptop's built-in speakers



--- Actual result ---
Silence



--- Hardware ---
I have a 'Dell XPS 15 (L502x)' laptop with:
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05)
	Subsystem: Dell Device 04b6
	Flags: bus master, fast devsel, latency 0, IRQ 53
	Memory at f1c00000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [50] Power Management version 2
	Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
	Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
	Capabilities: [100] Virtual Channel
	Capabilities: [130] Root Complex Link
	Kernel driver in use: snd_hda_intel



--- Bisection results ---
This was the output of the bisect:
---8<---------
80c8bfbe76869bfd6bdf3d260d316e7a32f318c3 is the first bad commit
commit 80c8bfbe76869bfd6bdf3d260d316e7a32f318c3
Author: David Henningsson <david.henningsson@canonical.com>
Date:   Mon Jun 4 09:33:51 2012 +0200

    ALSA: HDA: Create phantom jacks for fixed inputs and outputs
    
    PulseAudio sometimes have difficulties knowing that there is a
    "Speaker" or "Internal Mic", if they have no individual volume
    controls or selectors. As a result, only e g "Headphone" might
    be created for a laptop, but no "Speaker".
    To help out, create phantom jacks (that are always present,
    at least for now) for "Speaker", "Internal Mic" etc, in case we
    detect them.
    The naming convention is e g "Speaker Phantom Jack".
    
    In order not to pollute the /dev/input namespace with even more
    devices, these are added to the kcontrols only, not the input devices.
    
    Signed-off-by: David Henningsson <david.henningsson@canonical.com>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>

:040000 040000 7a954b731bef80cee731763521f64a424a7058a0 7d176b02ebb4553b0b0f97d200f7527cb69c122a M	sound
--->8---------

I tried to revert this commit on top of v3.6, but it would not apply.