[alsa-devel] Add AZX_DCAPS_I915_POWEREWELL on SKL is OK?

[Takashi Iwai]

At Thu, 26 Mar 2015 05:40:20 +0000,
Yang, Libin wrote:
> 
> Hi Takashi,
> 
> Is it OK to add AZX_DCAPS_I915_POWEREWELL for SKL in hda_intel.c?
> 
> SKL HDA controller is not in powerwell domain. But its 
> HDMI codec is in the domain. My understanding is if the flag
> is added here, it means the controller is in the domain. But I can't
> find a good place to add a flag to indicate the HDMI codec need
> the power domain.

The question is when you need the powerwell enable/disable.
If the powerwell has to be adjusted before *any* HDMI codec access,
we'd need this even at probing the codec.  Currently HD-audio
controller driver probes a codec by reading VENDOR_ID parameter of the
root node.  This was supposed to work even at codec D3, except for
Intel HDMI controllers.

Now, HDMI codec is on the common bus on SKL.  Does this mean that
reading the root node parameter works even without powerwell?
This has to be clarified at first.  I asked this in the last meeting,
but it seems still unclear.

If the root node parameter can be read without powerwell, then the
controller doesn't need it.  Instead, a similar code needs to be added
in the HDMI codec side.  OTOH, if the root parameter reads already
requires the powerwell, then yes, we need to add the DCAPS to the
controller.


Takashi