[ 5485.965788] [<c10041c0>] ? do_divide_error+0x0/0x90
[ 5485.980619] [<f87aa037>] ? pcm_pointer+0x37/0x70 [snd_echo3g]
[ 5485.998047] [<c104764e>] ? run_timer_softirq+0x17e/0x2e0
[ 5486.014175] [<f87ac9bf>] ? snd_echo_interrupt+0x11f/0x240 [snd_echo3g]
[ 5486.033940] [<c107a5d5>] ? handle_IRQ_event+0x45/0x190
bytes_to_frames() divides by runtime->frame_bits which is not set until
after the hw_params callback has succeeded, but the corresponding
chip->substream[] entry is set in that callback, by init_engine(). It
should probably have been set in the prepare callback.