Hi Liam,
I am facing an issue related to how DPCM manages state of back-end substream. Here is description of problem:
When front-end PCM substream is in paused state, back-end PCM substream will be put in paused state as well if given front-end PCM substream is the only client of given back-end. Based on current implementation of DPCM, when application closes front-end PCM substream, DPCM framework will not allow back-end enter HW_FREE state so back-end will never get shutdown completely as well.
refer to function soc_dpcm_be_dai_hw_free(), here is the check for states
if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_PARAMS) && (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PREPARE) && (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_FREE) && (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP)) continue;
Can't DPCM also allow back-end hardware being freed in STATE_PAUSED? Even if DPCM expects trigger stop coming to update back-end state to STATE_STOP, the following condition check will never allow back-end enter stop state anyway
Refer to soc_dpcm_be_dai_trigger()
case SNDRV_PCM_TRIGGER_STOP: if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START) continue;
Can you please take a look and recommend the appropriate state transition or it would be okay to allow PAUSED state in soc_dpcm_be_dai_hw_free()?
Thanks Patrick