I get a workable kernel of panda from linaro landing team, and after set alsa mixer properly, the sound will play well.
amixer cset name='DL1 Mixer Multimedia' 1
amixer cset name='DL1 Media Playback Volume' 118
amixer cset name='Sidetone Mixer Playback' 1
amixer cset name='SDT DL Volume' 120
amixer cset name='DL1 PDM Switch' 1
amixer cset name='HS Left Playback' 'HS DAC'
amixer cset name='HS Right Playback' 'HS DAC'
amixer cset name='Headset Playback Volume' 13
I update the mixer setting into alsa ucm configurations of panda.
BTW, in linaro release, i can't find udev rules for alsa-utils. So I'm not sure if "alsaucm set _verb HiFi" is called properly. In that case, you can call "sudo alsaucm set _verb HiFi" mannually