30.01.2020 17:09, Jon Hunter пишет: > > On 30/01/2020 04:38, Dmitry Osipenko wrote: >> It is enough to check whether hardware is busy on suspend and to reset >> it across of suspend-resume because channel's configuration is fully >> re-programmed on each DMA transaction anyways and because save-restore >> of an active channel won't end up well without pausing transfer prior to >> saving of the state (note that all channels shall be idling at the time of >> suspend, so save-restore is not needed at all). > > I guess if we ever wanted to support SNDRV_PCM_INFO_PAUSE for audio and > support the pause callback, then saving and restoring the channels could > be needed. Right now I believe that it will just terminate_all transfers > for audio on entering suspend. Any value in keeping this? Indeed, looks like [1] pauses DMA during suspend if SNDRV_PCM_INFO_PAUSE is supported. [1] https://elixir.bootlin.com/linux/v5.5/source/sound/core/pcm_dmaengine.c#L199 So we'll need to save-restore context only if DMA is in a paused state during suspend, I'll adjust this patch to do that and will see if enabling SNDRV_PCM_INFO_PAUSE works.
