[alsa-devel] HD-audio runtime PM

[Takashi Iwai]

At Tue, 10 Dec 2013 12:17:16 +0000,
Lin, Mengdong wrote:
> 
> Hi Takashi,
> 
> > -----Original Message-----
> > From: Lin, Mengdong
> > Sent: Monday, December 09, 2013 3:03 PM
> 
> > > > > I've checked two Haswell-ULT platforms with sound git tree
> > > > > for-linus
> > > > branch, under Ubuntu:
> > > > > - ELD cannot refresh properly.
> > > > > - HDMI hot-plug cannot wake up the audio controller.
> > 
> > I've tested the latest 3.13-rc2 based sound git tree, master branch:
> > - ELD can refresh properly on hot-plug event.
> >  I need to bisect to see where the ELD regression happened and how it
> > was fixed.
> 
> ELD info cannot refresh on hot-plug event after the controller enters D3 on Haswell.
> Sorry, I forgot to enable runtime PM yesterday when checking ELD refreshing.  
> 
> > - Headset insertion can wake up the legacy audio controller (PCI device
> > 00:1b)
> > 
> > - HDMI insertion still cannot wake up the display audio controller (PCI
> > device 00:03)  We'll double check with HW owner whether the display
> > audio controller really supports wake up on HDMI/DP insertion.
> >  I remember when Xingchao enabled runtime PM on Haswell display
> > audio controller for display power well release,  there was an issue that
> > this controller does not support "wake up", but we finally enable runtime
> > PM on it and remove the request for "wake up".
> 
> HW team clarified that HDMI/DP jack insertion cannot wake up the controller from D3. So this is a HW restriction for Haswell, not a driver regression.
> 
> Now the problem on Haswell/Broadwell is:
> After the controller enters D3, Gfx driver can still detect HDMI/DP hot plug event even if the display power well is disabled.
> Although Gfx driver set Presence Detect and ELD Valid , the audio controller does not wake up and so audio driver has no idea about the HDMI/DP hot-plug.
> 
> Is it audio driver itself or the user space that need this ELD info?
> Maybe Gfx driver can directly report ELD info to user space.

If so, the graphics driver can wake up the audio driver as well --
this is yet one more reason to create a direct communication channel
between the graphics and audio drivers :)


Takashi