Public bug reported:

Ever since the "up"grade to Ubuntu Natty, I have been having a host of
problems with regards to audio. Foremost among them is the unreliable
detection of sound related hardware during boot time. I have since done
a clean install (keeping only home folder, but deleting all
configuration other than Wine prefixes and virtual machines). The
problem persists even now.

The symptoms of the problem are thus: at boot time, 3 things may happen:
(1) the sound hardware (snd-hda-intel) will simply not be detected, (2)
the sound hardware is detected but the codec isn't (snd-hda-codec-
conexant) or (3) both are detected.

For cases (1) and (2), no sound is possible. Usually, but not always, I can get 
sound back by booting into a Lucid Live CD then booting back into Natty. For 
case (3), sound works, but is likely to stop working after a period of 
inactivity or with certain applications (Flash with Firefox, and Wine, are both 
reliable "killers" of audio); after audio stops working, I can get it back if I 
kill all programs that were using audio and run the following script:
echo "autospawn=no" > ~/.pulse/client.conf
pulseaudio -k
killall -q pulseaudio
sudo alsa force-reload
echo "autospawn=yes" > ~/.pulse/client.conf
pulseaudio -D

Sometimes, though, the above script will give the same results as case
(2) above, which leads me to believe the issues are related. I have
added the following lines to /etc/modprobe.d/alsa-base.conf (much as I
needed to since Karmic):

Top:
alias snd-card-0 snd-hda-intel
alias sound-slot-0 snd-hda-intel
install snd-hda-intel /sbin/modprobe --ignore-install snd-hda-intel 
$CMDLINE_OPTS

End:
options snd-hda-intel index=-2 power_save=0 power_save_controller=N

At the moment, I have been able to get only case (1) working; the output
of alsa-info.sh under these circumstances is here: http://www.alsa-
project.org/db/?f=f157afd6ad28a41962b9058b164b3bdbd0dbf9be

Yesterday, I was able to get sound fully working; under those
circumstances, alsa-info.sh returns this: http://www.alsa-
project.org/db/?f=28ff7b24dba70a86acc5e8ae6d2dd5ef3bf1220b

The difference between cases (2) and (3) is that the Conexant codec is not 
found; the hardware is found, but I only have a "Dummy output" available for 
selection. kern.log confirms this: when I run the script I gave above, the 
following lines are printed in case (2):
[112070.826937] HDA Intel 0000:00:07.0: PCI INT A -> Link[LAZA] -> GSI 21 
(level, low) -> IRQ 21
[112070.826942] hda_intel: Disable MSI for Nvidia chipset
[112070.827006] HDA Intel 0000:00:07.0: setting latency timer to 64
[112070.900039] hda-intel: no codecs found!
[112070.900099] HDA Intel 0000:00:07.0: PCI INT A disabled

But the following lines are printed in case (3):
[    5.858654] HDA Intel 0000:00:07.0: PCI INT A -> Link[LAZA] -> GSI 21 
(level, low) -> IRQ 21
[    5.858657] hda_intel: Disable MSI for Nvidia chipset
[    5.858717] HDA Intel 0000:00:07.0: setting latency timer to 64

If there is any further information I can give to help solve this
problem, please ask.

** Affects: ubuntu
     Importance: Undecided
         Status: New


** Tags: audio conexant hda intel natty

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https://bugs.launchpad.net/bugs/779983

Title:
  [Natty] Unreliable detection of snd-hda-intel with Conexant CX20549
  codec

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