[alsa-devel] HD-audio runtime PM

[Takashi Iwai]

At Tue, 26 Nov 2013 08:28:15 +0100,
Takashi Iwai wrote:
> 
> At Tue, 26 Nov 2013 06:56:12 +0000,
> Lin, Mengdong wrote:
> > 
> > > -----Original Message-----
> > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > Sent: Tuesday, November 26, 2013 2:14 PM
> > > To: Wang Xingchao
> >  
> > > > I test WAKEEN feature on Haswell machines before, it could really
> > > > wakeup system from D3.
> > > 
> > > But the runtime suspend doesn't power down to D3 by itself.
> > > Did you test really with D3?
> > 
> > I will double check this on Haswell with sound git tree for-linus branch.
> > We've tried Android on Haswell-ULT last week, the display HD-A controller can enter D3 and HDMI cable plug-in can wake up the controller and codec. The code base is v3.9 with various driver patches.
> 
> Hrm, but as I mentioned, we have no D3 call in runtime suspend
> callback.  How does it reach to D3 then?  Maybe that part is patched
> in your side?
> 
> > For non-Haswell platforms, hardware team suggest that unless all of the codecs on the HD-A link support EPSS and ClkStopOK, runtime PM of the controller should not be enabled on the controller. Otherwise, functionality will be lost and there are likely going to be audio artifacts.
> 
> Is EPSS mandatory?  We have already a check of ClkStopOK bit, but EPSS
> influences only on the wait time, so far.

I forgot that EPSS check does exist for HDMI codecs.  But it's not
applied to other codecs.


Takashi