On 30/01/2020 18:26, Dmitry Osipenko wrote: > 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 :) That's fine. We have lived with out it for this long. Jon -- nvpublic
