HD-Audio: ALSA settings not persistent across reboots.

stf92 · January 5, 2013, 10:23pm

Hi:
The OS is Slackware 14.0. When, after 14.0 install I first ran alsamixer, I got an error message and it quit. After some googling, I created /etc/modprobe.d/alsa.conf with these lines:

      alias snd-card-0 snd_hda_intel
      alias sound-slot-0 snd_hda_intel
      options snd_hda_intel model=auto

Then 'alsactl init' and 'alsactl store'.

All went well. I rebooted and still everything fine. I then turned off the computer and, this morning, after turning it on back, I found the OS had only found the PC builtin speaker but not the sound card, which is Realtek ALC887-VD (High definition audio). I ran alsa_utils_alsa-info.sh, provided by the ALSA project, and whose output I attach (alsa-info.txt.XXXXxjVB26_old.txt).

I renamed alsa.conf to a non existent name, rebooted, and all went back to normal. I renamed back to alsa.conf, rebooted again and still normal. See by the way /lib/modprobe.d/sound-modems.conf:

# ALSA modules to support sound modems.  These should be loaded manually
# if needed.  For most people they just break sound support...
blacklist snd-atiixp-modem
blacklist snd-intel8x0m
blacklist snd-via82xx-modem

In fact the detection of the sound card is random across reboots: sometimes detected, sometimes not. Perhaps removing the second line above has anything to do. Now, from HD-Audio.txt:

DMA-Position Problem

The most common problem of the controller is the inaccurate DMA
pointer reporting.  The DMA pointer for playback and capture can be
read in two ways, either via a LPIB register or via a position-buffer
map.  As default the driver tries to read from the io-mapped
position-buffer, and falls back to LPIB if the position-buffer appears
dead.  However, this detection isn't perfect on some devices.  In such
a case, you can change the default method via \`position_fix\` option.

\`position_fix=1\` means to use LPIB method explicitly.
\`position_fix=2\` means to use the position-buffer.
\`position_fix=3\` means to use a combination of both methods, needed
for some VIA and ATI controllers.  0 is the default value for all other
controllers, the automatic check and fallback to LPIB as described in
the above.  If you get a problem of repeated sounds, this option might
help.

Perhaps the addition of 'position_fix=3' in /etc/modprobe.d/alsa.conf, line options, solves the problem. I could try it myself, but I repeat, the behavior is almost random. In fact, in another post I saw some people used this option, but I disregarded it, because a remark there made reference to mic noise. Now, this is the output of alsa_utils_alsa-info.sh when everything goes well (see second attachment). That would be all, I think.

Slackware 14.0

EDIT: in /etc/modprobe.d/alsa.conf, I'm not sure if it is 'options snd_hda_intel' or 'snd-hda-intel'. Both forms get the same error message at boot time.

EDIT:

semoi@darkstar:/lib/modprobe.d$ cat sound-modems.conf 
##############################################################################
# Do not edit this file; instead, copy it to /etc/modprobe.d/ and edit that
##############################################################################

# ALSA modules to support sound modems.  These should be loaded manually
# if needed.  For most people they just break sound support...
blacklist snd-atiixp-modem
blacklist snd-intel8x0m
blacklist snd-via82xx-modem

semoi@darkstar:/lib/modprobe.d$

So, I just renamed /etc/modprobe.d/alsa.conf as /etc/modprobe.d/sound-modems.conf and appended the blacklist lines. Then booted and it worked. I must wait to see if it's still working after several boots [it is NOT]
As a side note, I think this post is not trivial if you believe, and I quote from another forum, this: