From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: [PATCH] ALSA: hda - Disable AA-loopback on ALC668
Date: Tue, 20 May 2014 18:06:53 +0200
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To: Gabriele Mazzotta <gabriele.mzt@gmail.com>
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At Tue, 20 May 2014 17:59:30 +0200,
Gabriele Mazzotta wrote:
> 
> On Thursday 15 May 2014 21:56:23, Gabriele Mazzotta <gabriele.mzt@gmail.com> 
> wrote:
> > On Wednesday 14 May 2014 16:31:13, Gabriele Mazzotta 
> <gabriele.mzt@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.


Takashi