When I upgraded tinyalsa to the new 2.0.0 major release (with breaking
changes) I failed to test q6voiced properly, even though I explicitly
had to rebuild it against the new tinyalsa version (see MR 1941).
In tinyalsa 2.0.0, calling pcm_open() does not automatically call
pcm_prepare() anymore, which is responsible for actually starting any
audio streams. This means that the old version of q6voiced is almost
entirely broken - only by pure luck it's sometimes possible to get
voice call audio working if you play other audio simultaenously while
a voice call is active. This does not work for the microphone though.
The new q6voiced version now calls pcm_prepare() explicitly to fix this.