ASoC q6asm race condition when stopping and preparing the stream

[Richard Acayan]

Hi,

There seems to be a race condition in q6asm when stopping the stream
(with uncompressed PCM). When receiving SNDRV_PCM_TRIGGER_STOP, the
driver sets the state to Q6ASM_STREAM_STOPPED and sends CMD_EOS to the
ADSP. If userspace decides to prepare the stream again in
q6asm_dai_prepare before receiving ASM_CLIENT_EVENT_CMD_EOS_DONE, the
memory-mapped region appears to still be in use and fails to map again.

I believe this race was observed since commit 81c53b52de21 ("ASoC: qcom:
qdsp6: q6asm-dai: set 10 ms period and buffer alignment."), but would
need to verify. On sdm670, we are coping downstream by keeping the state
as Q6ASM_STREAM_RUNNING until receiving CMD_EOS_DONE.

Can the ADSP emit DATA_WRITE_DONE or DATA_READ_DONE before CMD_EOS_DONE?
We might need an extra stopping state between CMD_EOS and CMD_EOS_DONE
so the driver doesn't request more data transfers.