30.01.2020 19:08, Dmitry Osipenko пишет: > 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. I started to look at it and found that the .device_pause() hook isn't implemented by the driver. So, it's fine to remove the context's save-restore for now. Jon, what about to keep this patch as-is? Later on I'll take a look at implementing the proper pausing functionality and try to cleanup code a bit further (remove the free list usage, etc).
