30.01.2020 21:06, Dmitry Osipenko пишет: > 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). Ah, only T114+ supports the per-channel pausing. So, I won't care about implementing the device_pause(), let's leave it to somebody else :)
