On 04-10-22, 13:58, Takashi Iwai wrote: > On Tue, 04 Oct 2022 13:18:15 +0200, > Daniel Baluta wrote: > > > > On Tue, Oct 4, 2022 at 12:46 PM Pierre-Louis Bossart > > <pierre-louis.bossart@xxxxxxxxxxxxxxx> wrote: > > > > > > On 10/4/22 11:07 AM, Daniel Baluta wrote: > > > > Hello all, > > > > > > > > It looks like system suspend is not implemented for Compress streams. > > > > > > > > Any story behind this? Were there any attempts on implementing this? > > > > > > It depends on the definition of 'system suspend'. > > > > > > What we had in mind back in the early 2010s was to allow for 'active > > > suspend' aka S0ix or low-power playback. That was the main reason for > > > introducing the API. > > > > > > For suspend to S3/D3, the plan was to just completely stop any > > > playback/capture and restart on resume. I am not sure if this was ever > > > implemented, that may be a miss. > > > > I see. Yes, we are looking at S3/D3 suspend and this doesn't look to > > be implemented. > > > > > > > > There is a corner case we may have overlooked. I am not sure what > > > happens if the S3/D3 suspend while playing. This is supported with e.g. > > > aplay but for the compressed case it's a bit more complicated. Not all > > > formats support rendering for a random position. > > > > True. We want to implement the same behavior as for aplay. Stop > > any playback/capture and restart on resume. There has been discussion in the past for this and as Pierre commented above it is really hard to resume a compressed stream. There is a big DSP dependency here.. > For PCM, basically the ALSA core doesn't fully "resume" unless the > driver explicitly implements it. It merely stops (drops) the stream, > sets the stream state to SNDRV_PCM_STATE_SUSPENDED, and lest the > user-space re-prepare and restart. Each driver is supposed to call > snd_pcm_suspend*() in the suspend callback, and basically that's all. > > I guess the same mechanism should be implemented for the compress > stream, too. Agree, based on DSP support a driver can opt in. Userspace should send the data as expected after resume. I dont think we can ever continue but it should be possible to restore at next frame or previous frame ... -- ~Vinod
