Anton Yakovlev
2021-Mar-02 15:35 UTC
[PATCH v6 9/9] ALSA: virtio: introduce device suspend/resume support
On 02.03.2021 10:11, Takashi Iwai wrote:> On Tue, 02 Mar 2021 09:09:33 +0100, > Anton Yakovlev wrote: >> >> On 02.03.2021 07:48, Takashi Iwai wrote: >>> On Tue, 02 Mar 2021 07:29:20 +0100, >>> Anton Yakovlev wrote: >>>> >>>> On 28.02.2021 13:05, Takashi Iwai wrote: >>>>> On Sat, 27 Feb 2021 09:59:56 +0100, >>>>> Anton Yakovlev wrote: >>>>>> >>>> >>>> [snip] >>>> >>>>>> --- a/sound/virtio/virtio_pcm.c >>>>>> +++ b/sound/virtio/virtio_pcm.c >>>>>> @@ -109,6 +109,7 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, >>>>>> SNDRV_PCM_INFO_BATCH | >>>>>> SNDRV_PCM_INFO_BLOCK_TRANSFER | >>>>>> SNDRV_PCM_INFO_INTERLEAVED | >>>>>> + SNDRV_PCM_INFO_RESUME | >>>>>> SNDRV_PCM_INFO_PAUSE; >>>>> >>>>> Actually you don't need to set SNDRV_PCM_INFO_RESUME. >>>>> This flag means that the driver supports the full resume procedure, >>>>> which isn't often the case; with this, the driver is supposed to >>>>> resume the stream exactly from the suspended position. >>>>> >>>>> Most drivers don't set this but implement only the suspend-stop >>>>> action. Then the application (or the sound backend) will re-setup the >>>>> stream and restart accordingly. >>>> >>>> I tried to resume driver without SNDRV_PCM_INFO_RESUME, and alsa-lib >>>> called only ops->prepare(). It makes sense for a typical hw, but we have >>>> "clean" unconfigured device on resume. And we must set hw parameters as >>>> a first step. It means, that code should be more or less the same. And >>>> maybe it's better to set SNDRV_PCM_INFO_RESUME, since it allows us to >>>> resume substream in any situation (regardless of application behavior). >>>> I can refactor code to only send requests from trigger(RESUME) path and >>>> not to call ops itself. It should make code more straitforward. What do >>>> you say? >>> >>> How about calling hw_params(NULL) conditionally in the prepare? >> >> Then the question is that condition. When ops->prepare() is called, the >> substream is in SUSPENDED state or not? If not then we need to track >> this in some additional field (and it will make logic a little bit >> clumsy, since that field is needed to be carefully handled in other >> places). > > Yes, you'd need to have a suspend/resume PM callback in the driver > that flips the internal flag to invalidate the hw_parmas, and in the > prepare callback, just call hw_params(NULL) if that flag is set. > >>> Doing the full stack work in the trigger callback is bad from the API >>> design POV; in general the trigger callback is supposed to be as short >>> as possible. >> >> Yeah, but usually original subsystem design does not take into account >> para-virtualized devices, which usually have it's own slightly different >> reality. And we need to introduce some tricks. > > The hardware drivers do a lot of more things in either suspend/resume > PM callbacks or prepare callback for re-setup of the hardware. We can > follow the similar pattern. Heavy-lifting works in the trigger > callbacks is really something to avoid.Ok, I redone this part and now the driver sets parameters for the device in ops->prepare() if the substream was suspended. And everything works fine. Thanks! I will send a new patch set soon.> Takashi >-- Anton Yakovlev Senior Software Engineer OpenSynergy GmbH Rotherstr. 20, 10245 Berlin