Bug#606482: no headphone output on ASUS M4A785T-D motherboard
* Jonathan Nieder [2012-02-25 21:19:43 -0600]:
> Sergio Gelato wrote:
>
> > The problem turned out to be due to an inappropriate BIOS configuration
> > setting. The "Front Panel Select" setting needed (for my specific case)
> > to be set to "AC97" instead of "HD Audio". Found thanks to some comments in
> > https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5309
> > (especially note 23449).
> >
> > No kernel changes needed.
>
> That sounds like a workaround rather than a fix.
I don't see it that way: my front panel is in fact of the older AC97 type,
so the earlier BIOS setting was incorrect and changing it was the proper
thing to do.
When I installed this motherboard I wasn't sure whether I had HDA or AC97,
so I decided to try one setting and see if it worked. The fact that the
Ubuntu 10.04 kernel appeared to work even with the setting I tried first
actually made it harder for me to correctly diagnose the problem.
> If it is possible to get the headphone jack working in HDA mode as well
> as AC97, we would like to do that, to avoid new users having to learn what
> BIOS knob to change.
That way lies madness. Maybe in this particular instance one can get away with
it, but in general this approach will add complexity to the software.
It's already bad enough to have to work around hardware bugs.
My impression so far is that the newer HDA front panels allow better power
management and that the driver change that apparently broke headphone sound
for me was actually an enhancement to make better use of the capabilities of
HDA. So of course one can revert to the older approach, but then one
probably loses some benefits of the newer one. One could add a kernel
(module) option to control this, but then the user needs to figure out what
setting is needed and it's just as easy to find out about the BIOS switch
instead.
My preferred approach would be to add this to the troubleshooting guides:
if your audio front panel is misbehaving, check that it is of the right type
for your motherboard. (Probably with some additional words about AC97 vs.
HDA and/or a link to an external reference.)
Now, if there was a way for the kernel to detect a misconfigured front panel
and issue a warning in dmesg that would be great. I have no idea whether that
is feasible.
> Based on the upstream report you mentioned it
> seems that 2.6.39 might fix this; could you try 3.2.y from wheezy or
> unstable? (The only packages needed from outside squeeze for this
> test are the kernel image itself, linux-base, and initramfs-tools.)
The reason I revisited this bug now is that I tried 3.2.0-0.bpo.1 (for
other reasons) and found that the headphone functionality was still
broken. That prompted me to make a new search through the ALSA knowledge
base, which yielded the hint about the two types of front panel. The
report I found the hint in ended up addressing some other issue.
> Thanks for the update,
> Jonathan
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