[alsa-devel] [PATCH] ALSA: hda - Disable AA-loopback on ALC668

[Takashi Iwai]

At Tue, 20 May 2014 18:06:53 +0200,
Takashi Iwai wrote:
> 
> At Tue, 20 May 2014 17:59:30 +0200,
> Gabriele Mazzotta wrote:
> > 
> > On Thursday 15 May 2014 21:56:23, Gabriele Mazzotta <gabriele.mzt at gmail.com> 
> > wrote:
> > > On Wednesday 14 May 2014 16:31:13, Gabriele Mazzotta 
> > <gabriele.mzt at gmail.com> wrote:
> > > I'm sorry, I was wrong. This patch does not help. I'm still trying to
> > > understand what temporarily fixed the problem, I was quite sure this patch 
> > did
> > > it, but all of the sudden the noise came back. I'm still trying to find the
> > > real cause, but I doubt I'll succeed.
> > > 
> > > Regards,
> > > Gabriele
> > I have to correct myself again, the first patch I submitted is working, I'm 
> > sorry. However, it seems that disabling the AA-loopback path is not necessary, 
> > muting the input 0x0b in node 0x0c (as it was suggested here: 
> > https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1252733/comments/26) is enough to get rid of the white noise.
> 
> This reminds me of a similar problem reported on Sony VAIO.
>   https://bugzilla.novell.com/show_bug.cgi?id=873704
> 
> The codec is different, it's ALC275, though.
> 
> > What is the proper way to fix this problem?
> 
> Just to be sure: does the mic input itself work correctly?
> 
> Maybe the easiest fix would be disabling the aamix, indeed.
> But you shouldn't apply it generically to ALC668.  I'm sure that it's
> pretty specific to machines, not codec chips.  So, create a fixup
> function that matches with your machine instead.

Or, another hackish solution is to override the connection list of the
mixer widget.  Point the item to another (e.g. non-existing) node, so
that the parser won't pick it up.

For this (and even with your patch to disable aamix completely), the
fixup should have a static init verb to mute this mixer input.


Takashi