Created attachment 919702 [details]
dmesg for kernel 3.15.6
Description of problem:
There is no sound with kernel 3.15.5 and 3.15.6
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Boot 3.15.5 or 3.15.6 kernel
Sound should be ok.
With kernel 3.14.8 there is no problem
Created attachment 919703 [details]
dmesg for kernel 3.14.8
Created attachment 919704 [details]
lspci for kernel 3.15.6
It looks like HDA intel audio is incorrectly detected as Conexant CX20561
[ 15.060156] sound hdaudioC0D2: CX20561 (Hermosa): BIOS auto-probing.
[ 15.060614] sound hdaudioC0D2: autoconfig: line_outs=1 (0x1a/0x0/0x0/0x0/0x0) type:speaker
[ 15.060618] sound hdaudioC0D2: speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
[ 15.060620] sound hdaudioC0D2: hp_outs=1 (0x16/0x0/0x0/0x0/0x0)
[ 15.060623] sound hdaudioC0D2: mono: mono_out=0x0
[ 15.060625] sound hdaudioC0D2: inputs:
[ 15.060628] sound hdaudioC0D2: Internal Mic=0x1d
[ 15.060630] sound hdaudioC0D2: Mic=0x18
[ 15.061311] sound hdaudioC0D2: Enable sync_write for stable communication
It turned out to be a PulseAudio bug which wrongly detects headphone as plugged-in and set Speaker Volume to 0% and Headphone Volume to 100%
If so, I'd strongly suggest taking this upstream to bugzilla.freedesktop.org pulseaudio component.
I'm not sure yet if it's PulseAudio bug or alsa bug. PulseAudio gets a notification from alsa about headphone plugged-in or unplugged. Maybe the notifications from alsa are not good.
It solved itself.