No echo of Microphone input

[shimi]

All,

I've recently purchased a new machine, with an ASUS M4N78 PRO
motherboard and have installed Gentoo Linux on it with Kernel 2.6.31
(upgraded later to 2.6.32 - no change).

Following is lspci output of Audio controllers:

$ /usr/sbin/lspci | grep Audio
00:07.0 Audio device: nVidia Corporation MCP72XE/MCP72P/MCP78U/MCP78S
High Definition Audio (rev a1)
02:00.1 Audio device: ATI Technologies Inc R700 Audio Device [Radeon
HD 4000 Series]

I believe the first device is my onboard audio card, and the second
device is the embedded audio out on the HDMI output of my ATI HD4670
video card.

Therefore, I am attaching the -v version of lspci on that specific card:

00:07.0 Audio device: nVidia Corporation MCP72XE/MCP72P/MCP78U/MCP78S
High Definition Audio (rev a1)
        Subsystem: ASUSTeK Computer Inc. Device 836c
        Flags: bus master, 66MHz, fast devsel, latency 0, IRQ 21
        Memory at fbe78000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [44] Power Management version 2
        Kernel driver in use: HDA Intel
        Kernel modules: snd-hda-intel

Now to my problem...

Everything seems to be working right. I can hear audio on all channels
(tried a 5.1 movie...), except for the echo output of the Microphone
input which I use to hear Television audio on my computer audio
system. At first I thought that I damaged the audio cable (it worked
on the old machine...), have bad motherboard connector or any other
similar thing, but after plugging in an mp3 player with a different
cable and still not even a hum, eventually I tried to *record* into a
file and then playback the result. To my surprise, I heard what was
earlier played into the Mic jack. I double/triple/quadruple checked in
alsamixer that all inputs are at maximum volume, including on the
capture device, and all are UNmuted, plus tried flipping between the
various "capture source"s to no avail.

After some more digging, googling et al, I've got to:
/usr/src/linux-`uname -r`/Documentation/sound/alsa/HD-Audio.txt

Specifically to the part of 'Model Option' as a possible culprit;
However, my specific model does not appear on the list, as far as I
could have seen; So I tried being generic, and added:

options snd_hda_intel model=6stack-digout bdl_pos_adj=32 single_cmd=1

To my /etc/modprobe.d/alsa.conf

My questions, if you got so far, are:

1. How do I know I did it right and that the module actually processed
these variables? The reason I am worried is because I still see the
error: "hda-intel: IRQ timing workaround is activated for card #1.
Suggest a bigger bdl_pos_adj." in dmesg.
2. Any hints on how to progress on this? Or should I get my old SB
Live 5.1 sound card and override the problem altogether...

Thanks in advance,

-- Shimi