[alsa-devel] New snd-hda warning spew

[Takashi Iwai]

On Mon, 21 Mar 2016 13:34:35 +0100,
Imre Deak wrote:
> 
> On la, 2016-03-19 at 11:18 +0100, Takashi Iwai wrote:
> > On Tue, 15 Mar 2016 18:22:56 +0100,
> > Takashi Iwai wrote:
> > > 
> > > On Tue, 15 Mar 2016 17:02:07 +0100,
> > > Ville Syrjälä wrote:
> > > > This other one was seen at least on on SKL:
> > > > [  124.808525] ------------[ cut here ]------------
> > > > [  124.808545] WARNING: CPU: 3 PID: 173 at
> > > > sound/hda/hdac_i915.c:91 snd_hdac_display_power+0xf1/0x110
> > > > [snd_hda_core]()
> > > 
> > > This is a different one, and it implies that the unbalanced power
> > > refcount.  Might be related with the recent fix for the recursive
> > > regmap deadlock.  I'll try later with a SKL machine here, too.
> > > 
> > > Didn't you see this before the recent tree, right?  Some good/bad
> > > commits would be really helpful...
> > 
> > So, we got a full log in bugzilla, and this looks like the on-demand
> > binding leading to the unbalanced refcount.
> > 
> > Could you try the patch below?  This essentially reverts to the 4.4
> > state, so a "regression" should be covered, at least.  It's applied
> > on
> > top of sound.git tree for-linus branch.  (But it should be easily
> > applicable to older trees, too.)
> > 
> > We need a proper fix later, but now more urgently the CI test
> > regression has to be papered over.
> 
> Looking more into this, it seems the root cause for this failure is
> that request_module returned pre-maturely (and with 0 return value)
> when i915 probing was still not finished. I tracked this issue down to
> the following kmod bug, fixed meanwhile upstream:
> http://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/?id=fd44a98ae2eb5eb32161088954ab21e58e19dfc4
> 
> Updating to the latest kmod fixed the issue. Things will of course work
> only in the general case where both the i915 and the sound driver are
> built as modules, to support other configurations we'd need to move the
> audio probing to happen at component bind time. 

Ah, good to know that the culprit is not only us! :)

I queued my temporary fix in anyway since the on-demand binding isn't
used any longer for 4.5/4.6.  It'll be re-added once when we take back
the support of eld notifier for old chips (which I'm currently working
on).  And then we'll be heading to the more stable component binding
with your patches to add component stub.


thanks,

Takashi