[alsa-devel] [PATCH 1/7] ASoC: Intel: Skylake: Add Resume capability in PCM info.

[Takashi Iwai]

On Thu, 26 Nov 2015 09:56:01 +0100,
Vinod Koul wrote:
> 
> On Tue, Nov 24, 2015 at 07:07:11AM +0100, Takashi Iwai wrote:
> > On Tue, 24 Nov 2015 03:44:49 +0100,
> > Vinod Koul wrote:
> > > 
> > > On Mon, Nov 23, 2015 at 07:45:20PM +0100, Takashi Iwai wrote:
> > > > On Mon, 23 Nov 2015 17:56:23 +0100,
> > > > Vinod Koul wrote:
> > > > > 
> > > > > From: Jeeja KP <jeeja.kp at intel.com>
> > > > > 
> > > > > This patch adds pcm capability to support Resume.
> > > > 
> > > > The flag indicates that the driver is capable of the full resume --
> > > > i.e. it must resume everything at the exactly same point to be
> > > > suspended.  Is it really the case?
> > > > 
> > > > If it's not and it's instead a kind of restart of streams, don't add
> > > > this flag.  The lack of the flag doesn't mean that the driver can't
> > > > resume at all.
> > > 
> > > Yes, with this patch series we are able to resume from previous position.
> > 
> > I suppose you tested hibernation, too?
> 
> No, only suspend and freeze
> 
> > How does it assure that the in-flight data on FIFO are restored after
> > the link reset and re-prepare?
> 
> SKL has DMA resume capability, so we can restore the registers, Jeeja is
> preparing those patches and we should be able to send those shortly :)

Well, the question is about hibernation.  Then the in-flight data on
the device is basically gone, and we can handle only the remaining CPU
data.  If your DMA can do that, it's fine, we can go in that way.

> > > Here is my test:
> > > 
> > > # aplay -Dhw:0,0 play.wav
> > > Playing WAVE 'play.wav' : Signed 16 bit Little Endian, Rate 48000 Hz,
> > > Stereo
> > > Suspended. Trying resume. Done.
> > 
> > As mentioned, the resume usually works (sort of), even without
> > SNDRV_PCM_INFO_RESUME bit.  It's because alsa-lib tries to re-prepare
> > the stuff by itself.
> > 
> > Did you try only the patch 2 without this patch?
> 
> Yes Jeeja did that and in that case it does prepare and resumes

That's the expected result.  As a fallback, user-space expects
prepares and restarts.


Takashi