Asus C101PA headphone jack problem

[watanabek]

I installed ArchLinux ARM into Asus C101PA.
I followed this instruction (It worked).
https://archlinuxarm.org/platforms/armv ... lip-c101pa
After that, I installed lightdm, mate-desktop, firefox, alsa, pulseaudio, and so on,
and followed this additional configuration
https://archlinuxarm.org/platforms/armv ... ebook-plus
then, volume control has been corrected.
It seems perfect with the internal speakers.

But, Headphone jack is not working.
If I connect my headphone to the jack, nothing happens,
the sound is output from internal speakers.

Can I fix this?