Hi,
On Via codecs reported on https://bugs.launchpad.net/bugs/1052499, while investigating the report, it can be seen that on Headphone pin the plug is not detectable (NO_PRESENCE). It could be that front panel is AC97 wiring or something else, I don't know. But it makes the jack detection handling code to add the headphone jack as "phantom", which makes snd_hda_jack_detect return headphone jack as always present (commit 80c8bfbe768 is applied/cherry-picked on the reported kernel).
Thus after jacks are added, the automute code will always detect HP as present, and keep muted all line-outs. The proposed solution following this is using is_jack_detectable inside via_hp_automute to handle this, other codecs seem to use also is_jack_detectable at the moment in similar situations. Other approach could be also to not report presence on phantom jacks with HP or Line Outs.
-- []'s Herton